=Paper= {{Paper |id=Vol-3682/Paper11 |storemode=property |title=CGM: A hybrid model for forecasting future stock price |pdfUrl=https://ceur-ws.org/Vol-3682/Paper11.pdf |volume=Vol-3682 |authors=Ningyao Ningshen,Vinita Jindal,Punam Bedi |dblpUrl=https://dblp.org/rec/conf/sci2/NingshenJB24 }} ==CGM: A hybrid model for forecasting future stock price== https://ceur-ws.org/Vol-3682/Paper11.pdf
                                CGM: A hybrid model for forecasting future stock price
                                Ningyao Ningshen1, *, Vinita Jindal2 and Punam Bedi1

                                1 Department of Computer Science, University of Delhi, New Delhi, India, 110007

                                2 Department of Computer Science, Keshav Mahavidyalaya, University of Delhi, New Delhi, India, 110034




                                                Abstract
                                                In finance, Forecasting Stock Price (FSP) poses a significant challenge. However,
                                                the swift progress enabled by Artificial Intelligence (AI) techniques,
                                                particularly Deep Neural Network (DNN) has propelled the advancements in
                                                this sector. Consequently, researchers have investigated the application of
                                                different DNN techniques. Despite these efforts, existing models are often
                                                shallow and prone to overfitting due to the model's complexity. Consequently,
                                                there is still room for improvement in achieving accurate forecasts of the future
                                                closing price. Therefore, to advance FSP, a novel hybrid model named CGM is
                                                proposed, which is developed using a combination of Convolution, Gated
                                                Recurrent Unit (GRU), and Multi-Layer Perceptron (MLP). Thereafter, the CGM
                                                model is trained using technical features, Intrinsic Mode Function (IMF)
                                                decomposed using Empirical Mode Function (EMD), and a combination of both
                                                to exhaustively explore the ability of the CGM model, thus producing three
                                                distinct models, namely TF-CGM, IMF-CGM, and TF-IMF-CGM models.
                                                Furthermore, to automatically tailor the hyperparameters of the
                                                aforementioned models, Neural Architectural Search (NAS) is employed to
                                                automatically fine-tune the hyperparameters of the models. During the
                                                experiment, the aforementioned models are evaluated using Root Mean Square
                                                Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage
                                                Error (MAPE) evaluation metrics using stock indices listed in the New York
                                                Stock Exchange (NYSE) and National Stock Exchange (NSE). From the
                                                experimental results, it was observed that technical features exert a more
                                                significant influence, which leads to the TF-CGM model outperforming the IMF-
                                                CGM and TF-IMF-CGM models. Moreover, the proposed models provided better
                                                performance when compared with existing models present in the literature.

                                                Keywords
                                                Finance, Artificial Intelligence, Machine Learning, Deep Neural Network, Gated Recurrent Unit,
                                                Multi-Layer Perceptron1




                                Symposium on Computing & Intelligent Systems (SCI), May 10, 2024, New Delhi, INDIA
                                ∗ Corresponding author.
                                † These authors contributed equally.

                                   nningshen@cs.du.ac.in (N. Ningshen); vjindal@keshav.du.ac.in (V. Jindal); pbedi@cs.du.ac.in (P. Bedi)
                                    0009-0003-8909-8648 (N. Ningshen); 0000-0002-0481-4840 (V. Jindal); 0000-0002-6007-7961 (P. Bedi)
                                           © 2024 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).




CEUR
                  ceur-ws.org
Workshop      ISSN 1613-0073
Proceedings
1. Introduction
    Predicting future stock prices and market indices is crucial for investors and traders
seeking positive returns on their investments. However, it remains a challenge due to the
complex dynamics influenced by economic, emotional, and political factors, as suggested by
the Efficient Market Hypothesis (EMH). Despite this, efforts have been made to develop
strategies for successful price prediction [1]. Traditionally, Forecasting Stock Price (FSP)
involves examining historical price movement and trading volumes together with a
comprehensive assessment of a company’s financial health to ascertain its intrinsic value
and potential for future growth. However, such methods presume the presence of
exploitable trends in historical data for forecasting future prices. Therefore, an alternative
method such as statistical models like Auto-Regressive Integrated Moving Average (ARIMA)
and Seasonal ARIMA (SARIMA) are commonly utilized for future price forecasting [2], [3],
[4]. Nevertheless, the linearity inherent in these statistical models limits their ability to
capture the complex dynamics exhibited by historical market data. Consequently, various
researchers have explored the usage of Deep Neural Network (DNN) in FSP [1], [5], [6], [7],
[8]. However, due to the shallow nature of the existing models, they are susceptible to
overfitting. Therefore, this research paper aims to address this limitation by proposing a
novel hybrid model named CGM, which employs a combination of Convolution, Gated
Recurrent Unit (GRU), and Multi-Layer (MLP) Perceptron techniques.
    A convolutional layer is a building block of a Convolutional Neural Network (CNN) [9],
which is widely used in image analysis. It involves a convolution operation, wherein filters
slide across the input data, performing an element-wise multiplication between the filter
and the input to extract localized spatial information. Meanwhile, GRU, introduced by [10],
is a category of Recurrent Neural Networks (RNN), which is specifically designed to address
the challenges of RNN in capturing long-range dependencies. Furthermore, MLP, a type of
fully connected feedforward ANN is also utilized in the development of the CGM model.
During the experiment, the hybrid CGM model is trained using three different types of
inputs i.e., Technical Features (TFs), Intrinsic Mode Functions (IMFs), and a combination of
both features, thereby producing three unique variants of the CGM model, namely TF-CGM,
IMF-CGM, and TF-IMF-CGM models. Furthermore, the Neural Architectural Search (NAS)
algorithm [11], which is a subfield in Machine Learning (ML) for streamlining the ML
pipeline is introduced to facilitate automatic hyperparameter tuning in the TF-CGM, IMF-
CGM, and TF-IMF-CGM models.
    The manuscript is divided into six sections. Section 2 presents the summary of the
existing literature centered on stock price prediction using DNN techniques. Sections 3 and
4 delve into the proposed work and its experimental study, which is followed by presenting
the results and discussion of the experiment in Section 5. Finally, Section 6 presents the
conclusion of the research work.

2. Literature Review
   In the last decade, researchers have increasingly turned to DNN for stock price
prediction, leveraging their capability to capture non-linear dependencies in financial time
series data. In the research work conducted by Selvamuthu et al., (2019), three learning
techniques, namely Levenberg-Marquardt (LM), Scaled Conjugate Gradient (SCG), and
Bayesian Regularization (BR) were explored. Their experimental results, assessed using
both tick data and 15-minute data revealed that SCG exhibited superior performance in
comparison to LM and BR. However, the authors concluded that incorporating LSTM and
integrating sentiment analysis could potentially yield better results. In a comparable
investigation carried out by Cao et al., (2019), time-series financial data underwent
decomposition into IMFs through the application of both Empirical Mode Decomposition
(EMD) and Complete Ensemble Mode Decomposition with Adaptive Noise (CEEMDAN)
techniques, and its influence was assessed using a two-layered LSTM model. They observed
that two-layered LSTM outperformed one-layered LSTM, MLP, and Support Vector Machine
(SVM). Moreover, Chen et al., (2019) explored the application of the attention mechanism
in LSTM for stock market prediction. Their experiment was verified using the SSE stock
index and found that LSTM with an attention mechanism has more potential, thereby
achieving better results compared to standalone LSTM. In the subsequent research work
conducted by Shen & Shafiq, (2020), the effectiveness of LSTM was investigated in short-
term trend forecasting for market prices. Their approach encompassed feature expansion
steps using min-max scaling, polarization, and computing percentage fluctuation. They
contended that the superiority of their model over others stems from the comprehensive
feature engineering employed in their methodology. Taking a different approach, Yang et
al., (2020) leveraged three-dimensional CNN to extract features from stock data meanwhile,
LSTM was used for prediction. However, they opted to exclude the pooling layers in their
experiment to prevent potential information loss. Their findings underscored the
significant role of ranking stock indices in enhancing the overall performance of their
models.
     In a more recent study conducted by Ji et al., (2021), an LSTM model was proposed for
stock price prediction. Their study involved decomposing the stock data into deterministic
signals through wavelet transform techniques. Additionally, sentiment analysis was
incorporated by utilizing text data acquired from social media. Their experimentation
demonstrated success when compared to traditional models. To emphasize the significance
of utilizing DNN in forecasting future metal prices in the metal industry, Lin et al., (2022)
proposed a novel model that is based on Modified Ensemble Empirical Mode Decomposition
(MEEMD) and LSTM. They pointed out that MEEMD demonstrated a better decomposition
effect than EMD. In [19], a novel architecture named FDGRU-transformer (Frequency
Decomposition induced Gate Recurrent Unit Transformer) was proposed to tackle the stock
price prediction problem. Their method involved decomposing stock data into IMFs using
the EMD technique. Furthermore, a GRU, LSTM, and multi-head attention were utilized to
extract temporal information. Their model’s comparison with existing state-of-the-art
models indicated better results. Moreover, as a consequence of ANN’s popularity in FSP,
Seabe et al., (2023) explored the capability of LSTM, GRU, and bi-directional LSTM in
forecasting the price of Bitcoin, Ethereum, and Litecoin. Their model’s evaluation illustrated
that bi-directional LSTM possesses the highest capability in predicting the prices of the
cryptocurrencies.
    Despite the success in the application of DNN in FSP, the existing models are often
characterized by limited depth, potentially leading to overfitting. Therefore, to address this
limitation and enhance the prediction accuracy, this research work introduces a novel
hybrid model, named CGM by integrating Convolution, GRU, and MLP techniques.
Furthermore, to achieve a balance between model prediction performance and
representativeness in architectural configurations, the NAS algorithm is employed to
automatically optimize hyperparameters, eliminating the need for manual hyperparameter
tuning. A detailed description of the proposed hybrid CGM model is presented in the
following section.

3. Proposed CGM model
   Conventional methods such as time series analysis and statistical approaches have
established the groundwork for comprehending market dynamics. However, due to the
subjective and non-linear characteristics inherent in traditional approaches, contemporary
methodologies like DNN techniques offer more promising alternatives for FSP. Nonetheless,
existing DNN models are often shallow, and susceptible to overfitting. Therefore, this
research work aims to contribute to the ongoing discourse by proposing a novel hybrid
model, named CGM, which stands for Convolution, GRU, and MLP respectively. The
proposed hybrid CGM model (given in Figure 1) comprises an Input block, a Conditional
block, and an Output block. The components are discussed below.




                   Figure 1. Visual representation of the hybrid CGM model


3.1. Input block
    The Input block of the CGM model incorporates Convolution, GRU, and MLP modules.
The Convolution module consists of four Convolutional layers. The initial layer establishes
a connection with the input layer. Subsequently, the output is concurrently fed into three
parallel Convolutional layers, capturing various aspects and representations of the input
data. In tandem with the Convolution module, the Input block also integrates a GRU module
to learn feature dependencies over long ranges. Similar to the Convolution module, the first
GRU layer establishes a connection with the input layer. The resulting output is then
directed to two subsequent GRU layers for further processing, and their outputs are
aggregated before being forwarded to subsequent layers. Additionally, to augment feature
extraction capability, an MLP module is also employed, comprising three Dense layers.
Analogous to the aforementioned modules, the initial Dense layer receives input from the
input layer and its output is concurrently transmitted to two Dense layers. The resulting
outputs are amalgamated and forwarded for subsequent processing. The visual
representation of the Convolution, GRU, and MLP modules of the Input block are given in
Figure 2 (a), (b), and (c) respectively.




                 Figure 2. (a) Convolution, (b) GRU, and (c) MLP modules.

3.2. Conditional and Output block
    In the Conditional block, three sets of Dropout and Normalization layers are arranged
parallelly to improve training stability, prevent overfitting, and further enhance the overall
performance of the model. The input of the Conditional block is derived from the
Convolution, GRU, and MLP modules of the preceding block. Each of these modules feeds
independently into the corresponding Dropout and Normalization layers within the
Conditional block. The visual representation of the Conditional block is given in Figure 3 (a).
    After the Conditional block, the outputs are forwarded to the Output block. The Output
block consists of Concatenation, Bi-directional GRU, and Dense Layers. The Concatenation
layer concatenates the input received from the Conditional block to create a unified feature
yielding a more comprehensive feature representation of the input. The concatenation steps
follow the procedure given in Equation 1.


                              𝑔(𝑛1 , 𝑛2 , 𝑛3 ) 𝑖𝑓 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑏𝑙𝑜𝑐𝑘 = 𝑇𝑟𝑢𝑒
                𝑥𝑐𝑜𝑛𝑐𝑎𝑡 = {                                                                 (1)
                              𝑔(𝑐1 , 𝑐2 , 𝑐3 )                   𝑂𝑡ℎ𝑒𝑟𝑤𝑖𝑠𝑒

where g is the concatenation operation, 𝑛1 , 𝑛2 , 𝑛3 are the outputs from conditional block
and 𝑐1 , 𝑐2 , 𝑐3 are outputs produced by Convolution, GRU, and MLP modules. The visual
representation of the Output block is given in Figure 3 (b).
   Following the concatenation step, the combined output is passed through a bidirectional
GRU layer to handle input from both forward and backward directions. This enables the
model to grasp both past and future context, facilitating the model to capture bi-directional
dependencies within the data. Ultimately, the resulting output is directed to the final Dense
layer with a sigmoid function for predicting the future stock price.




                    Figure 3. (a) Conditional block and (b) Output block

   Throughout the experiment, three models undergo fine-tuning and training using TFs,
IMFs, and combinations of both TFs and IMFs. This process leads to the development of
three distinct CGM models: TF-CGM, IMF-CGM, and TF-IMF-CGM, where TFs are fed as input
to TF-CGM, IMFs into IMF-CGM, and TF+IMFs into TF-IMF-CGM models. Henceforth, we will
refer to these models individually as TF-CGM, IMF-CGM, and TF-IMF-CGM. Furthermore, to
streamline the experimentation process and eliminate manual hyperparameter tuning for
the aforementioned models, the NAS algorithm is employed. This algorithm automatically
determines hyperparameters such as learning rate, activation function, hidden units,
number of filters, and the decision to include or exclude a conditional block during training.
The detailed results of the conducted experiment are discussed in the following section.

4. Experimentation
   This section provides an in-depth exploration of the experiments carried out during the
research study. The primary goal of the research is to develop a hybrid model that is
expressive enough (i.e., a representable number of trainable parameters) as well as improve
the performance of predicting future stock prices, thus striking a balance between
complexity and performance.

4.1. Data collection and preprocessing
   In the course of the study’s experimentation, daily OHLCV of four stock indices listed in
the New York Stock Exchange (NYSE) and four stock indices listed in the NSE are collected
from Yahoo Finance for training and testing.
   Furthermore, during the data preparation, NaN (not a number) values are dropped from
the dataset. Subsequently, lag features with a window size of 5 were constructed from the
independent features. Additionally, the stock data was decomposed into IMFs using the
EMD technique as described in [21]. Subsequently, the time-series data is reorganized to
embed temporal information into the dataset. Naturally, 𝑥𝑡,𝑓 ∈ 𝑋 denotes a singular input,
where 𝑥𝑡,𝑓 represents data at time t with features f. However, during the experiment of this
research work, the input sample 𝑥𝑖 and label 𝑦𝑖 is reconfigured as 𝑥𝑖 =
{𝑥𝑡+𝑖 , 𝑥𝑡+𝑖+1 , … , 𝑥𝑡+𝑖+𝑛 } and 𝑦𝑖 = {𝑦𝑡+𝑖+𝑛+1 }, where the window size n is equal 10.
Moreover, each sample is normalized using a Min-Max Scaler [22]. Following the data
preprocessing, the data are split into training, validation, and testing subsets in a ratio of
7:2:1.

4.2. Experimental configuration and evaluation metrics
   During the experimentation, the TF-CGM, IMF-CGM, and TF-IMF-CGM models were
experimented on a Metal Performance Shader (MPS) device. Furthermore, throughout the
experiment, Python v3.11 was used as a primary language, and TensorFlow v2.15 as the ML
framework. Nonetheless, different programming languages and frameworks could be used
for the experiment.
   In the initial step of the experiment, the NAS algorithm was used to optimize the
hyperparameters of the aforementioned models independently. The NAS algorithm utilizes
a RandomSearch technique to determine the value of the hyperparameters. The process
involved conducting 10 trials, each comprising four runs to optimize the loss function.
Subsequently, the optimized TF-CGM, IMF-CGM, and TF-IMF-CGM were trained using TFs,
IMFs, and a combination of TFs and IMFs for forecasting the future close price of daily stock
data. The models were trained for 250 epochs with a batch size of 32. Moreover, an early
stopping mechanism is employed during training to prevent the models from overfitting
with a patience of 30 epochs i.e., the training stops if there is no sign of improvement for 30
successive epochs. Furthermore, Adam [23] optimizer was utilized to minimize the loss
function associated with the models.
   During the experiment, the Mean Square Error (MSE) given in Equation 2 was used as a
loss function to measure the performance of each trial. However, Root Mean Squared Error
(RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) were
used to evaluate the performance of the models during the training and testing phase. The
mathematical formulae for the metrics are given in Equation 3 – 5.

                                                n
                                          1
                                     𝑀𝑆𝐸 = ∑(yi − ŷi )2                                    (2)
                                          n
                                               i=1
                                        RMSE = √MSE                                         (3)

                                           ∑ni=1|yi − ŷi |
                                      MAE =                                                 (4)
                                                 n
                                              n
                                           1      yi − ŷi
                                     MAPE = ∑ |             |                               (5)
                                           n         yi
                                                i=1
5. Results and Discussion
   This section presents the results of the hybrid CGM model in predicting the future close
price of daily stock data. As previously stated, three variations of the hybrid CGM model,
namely TF-CGM, IMF-CGM, and TE-IMF -CGM underwent hyperparameters tuning
individually. The results of the NAS algorithm during hyperparameter optimization for the
aforementioned models are given in Table 1.

Table 1. Hyperparameters selected by the NAS algorithm during hyperparameter tuning
   Hyperparameters                 TF-CGM            IMF -CGM           TF-IMF-CGM
   Activation Function             gelu              gelu               gelu
   Learning Rate                   5.434e-4          1.089e-4           2.598e-4
   Dropout Layer                   True              False              True
   Normalization Layer             True              False              False
   GRU units                       192               160                128
   MLP units                       192               160                128
   Convolution filter size         160               32                 64
   Trainable Parameters            1, 587, 493       955, 137           678, 849

   From the results presented in Table 1, it is evident that the model favors gelu as the
activation function compared to other activation functions. Furthermore, the
hyperparameter tuning performed by the NAS algorithm consistently opts for a low
learning rate. However, the determination to include or exclude the conditional block is
contingent on the variant of the model. Subsequently, the models were evaluated on NYSE
and NSE stock data using RMSE, MAE, and MAPE evaluation metrics. The results of TF-CGM,
IMF-CGM, and TE-IMF-CGM on the test set are given in Table 2 and 3.
   The analysis of Table 2 and 3 leads to the conclusion that TF-CGM exhibited superior
performance when compared to IMF-CGM and TF-IMF-CGM. Additionally, the Linear
Regression Analysis (LRA) on NYSE and NSE shown in Figure 4 further substantiates the
supremacy of TF-CGM over IMF-CGM and TF-IMF-CGM in forecasting the future closing
prices of daily stock data. Furthermore, to bolster the claim of the proposed model's
superiority, the performance of the models was compared with models documented in the
existing literature given in Table 3.

Table 2. Evaluation results of TF-CGM, IMF-CGM, and TF-IMF-CGM models on NYSE stock
indices.
            Ticker       Model                   RMSE        MAE          MAPE
                         TF-CGM                   3.47       2.58         0.037
            AAPL         IMF-CGM                  4.89       3.08         0.030
                         TF-IMF-CGM               2.79       2.79         0.030
                         TF-CGM                   2.24       1.63         0.022
            ABT          IMF-CGM                  3.45       2.45         0.029
                         TF-IMF-CGM               2.97       2.13         0.026
                         TF-CGM                   6.20       4.73         0.030
           MSFT        IMF-CGM              9.75       6.34        0.030
                       TF-IMF-CGM           8.29       5.42        0.026
                       TF-CGM               3.82       2.41        0.063
           AMD         IMF-CGM              2.84       1.53        0.041
                       TF-IMF-CGM           4.09       2.38        0.060
                       TF-CGM               3.93       2.83        0.038
           Mean        IMF-CGM              5.23       3.35        0.032
                       TF-IMF-CGM           4.53       3.18        0.035



Table 3. Evaluation results of TF-CGM, IMF-CGM, and TF-IMF-CGM models on NSE stock
indices.
            Ticker              Model          RMS         MAE        MAPE
                                               E
          RELIANCE             TF-CGM         65.34        49.24       0.027
                              IMF-CGM         106.01       82.54       0.038
                             TF-IMF-CGM       91.56        72.12       0.037
        TATACONSUM             TF-CGM         17.57       13.056       0.028
                              IMF-CGM         31.77        22.93       0.036
                             TF-IMF-CGM       22.33        16.41       0.031
             SBIN              TF-CGM         14.35        10.87       0.032
                              IMF-CGM         19.61        13.46       0.031
                             TF-IMF-CGM       17.58        13.40       0.036
            CIPLA              TF-CGM         24.19        16.84       0.022
                              IMF-CGM         36.49        25.16       0.028
                             TF-IMF-CGM       35.99        27.94       0.035
                               TF-CGM         30.36        22.50       0.027
             Mean             IMF-CGM         48.47        36.02       0.033
                             TF-IMF-CGM       41.86        32.46       0.034
Figure 4. Linear Regression Analysis of TF-CGM, IMF-CGM, and TF-IMF-CGM on NYSE and
NSE stock indices.

   The analysis of Table 2 and 3 leads to the conclusion that TF-CGM exhibited superior
performance when compared to IMF-CGM and TF-IMF-CGM. Additionally, the Linear
Regression Analysis (LRA) on NYSE and NSE shown in Figure 4 further substantiates the
supremacy of TF-CGM over IMF-CGM and TF-IMF-CGM in forecasting the future closing
prices of daily stock data. Furthermore, to bolster the claim of the proposed model's
superiority, the performance of the models was compared with models documented in the
existing literature given in Table 4.

Table 4. Performance comparison of the proposed hybrid model with the models present in
the existing literature. The given scores for TF-CGM, IMF-CGM, and TF-IMF-CGM are the
mean of the scores obtained in the NYSE and NSE stock indices given in Table 2 and 3.
    Model                                            RMSE        MAE       MAPE
    [12] (SCG+ANN)                                   -           -         99.908
    [14] (EMD+LSTM+ATTENTION)                        26.10       16.39     0.66
    [24] (Convolution+LSTM)                          386.47      -         -
    [25] (LASSO-GRU)                                 27.45       19.14     -
    [20] (bi-LSTM)                                   373.77      -         0.067
    [26] (GRU)                                       0.084       22.94     0.259
          TF-CGM (proposed)                                    17.14        12.66      0.032
          IMF-CGM (proposed)                                   26.85        19.68      0.032
          TF-IMF-CGM (proposed)                                23.19        17.82      0.033

         From the results presented in Table 2 and 3, it can be concluded that TF-CGM
      outperforms IMF-CGM and TF-IMF-CGM, emphasizing the significant impact of technical
      factors on the model. Additionally, the models display reduced efficacy when applied to NSE
      data, as indicated by higher RMSE and MAE values, signifying a relatively larger margin of
      error. However, the models exhibit relatively similar MAPE values on NSE data, which
      indicates comparatively similar relative size errors in accuracy. The disparity in the scores
      of TF-CGM, IMF-CGM, and TF-IMF-CGM on NYSE and NSE data implies variations in the
      factors influencing the NYSE and NSE markets. Therefore, future research could involve
      exploring market dynamics and examining the variables that affect the performance of the
      models. Moreover, sentiment analysis could also be integrated to further enhance the
      predictive capability of the models.

      6. Conclusion
         Forecasting future stock prices poses a significant challenge in the financial sector, and
      addressing this challenge has been an active area of research. Hence, various researchers
      have contributed to this field by developing models using modern DNN techniques.
      However, existing models tend to be shallow and susceptible to overfitting. To address this
      challenge, this research paper proposes a hybrid CGM model that incorporates Convolution,
      GRU, and MLP techniques.
         Moreover, to comprehensively assess the effectiveness hybrid CGM model, three
      different inputs – TFs, IMFs, and a combination of both – were used to train the CGM model,
      resulting in three distinct models, namely TF-CGM, IMF-CGM, and TF-IMF-CGM models.
      Furthermore, to tackle the challenges associated with tailoring the hyperparameters of the
      models, the NAS algorithm was employed to automatically optimize the hyperparameters.
      These models were then trained and tested using four stock indices listed in the NYSE and
      four stock indices listed in the NSE. Thereafter, the performance of the models was
      evaluated using RMSE, MAE, and MAPE metrics. From the experiment, it was found that TF-
      CGM outperformed the IMF-CGM and TF-IMF-CGM models by scoring 3.93, 2.83, and 0.038
      on NYSE data, and 30.36, 22.50, and 0.027 on NSE data respectively for the aforementioned
      evaluation metrics. Moreover, the proposed models were compared with existing models,
      the proposed models demonstrated superior performance.


      References
[1]   P. M. Tsang et al., “Design and implementation of NN5 for Hong Kong stock price
      forecasting,” Eng Appl Artif Intell, vol. 20, pp. 453–461, 2007, doi:
      10.1016/j.engappai.2006.10.002.
[2]    A. A. Adebiyi, A. O. Adewumi, and C. K. Ayo, “Stock price prediction using the ARIMA model,”
       Proceedings - UKSim-AMSS 16th International Conference on Computer Modelling and
       Simulation, UKSim 2014, pp. 106–112, 2014, doi: 10.1109/UKSIM.2014.67.
[3]    Daryl, A. Winata, S. Kumara, and D. Suhartono, “Predicting Stock Market Prices using Time
       Series SARIMA,” Proceedings of 2021 1st International Conference on Computer Science and
       Artificial      Intelligence,       ICCSAI      2021,      pp.      92–99,       2021,    doi:
       10.1109/ICCSAI53272.2021.9609720.
[4]    S. Khanderwal and D. Mohanty, “Stock Price Prediction Using ARIMA Model,” International
       Journal of Marketing & Human Resource Research, vol. 2, no. 2, pp. 98–107, Apr. 2021,
       Accessed:       Dec.     18,      2023.    [Online].    Available:    https://www.journal.jis-
       institute.org/index.php/ijmhrr/article/view/235
[5]    K. Alkhatib, H. Najadat, I. Hmeidi, and M. K. A. Shatnawi, “Stock Price Prediction Using K-
       Nearest Neighbor (KNN) Algorithm,” International Journal of Business, vol. 3, no. 3, 2013,
       Accessed: Dec. 18, 2023. [Online]. Available: www.ijbhtnet.com
[6]    S. Mehtab, J. Sen, and A. Dutta, “Stock Price Prediction Using Machine Learning and LSTM-
       Based Deep Learning Models,” in SOMMA, vol. 1366, 2021, pp. 88–106. doi: 10.1007/978-
       981-16-0419-5_8.
[7]    J. Sen, “Stock Price Prediction Using Machine Learning and Deep Learning Frameworks,” in
       ICBAI, 2018.
[8]    X. Zhang, Y. Huang, K. Xu, and L. Xing, “Novel modelling strategies for high-frequency stock
       trading data,” Financial Innovation, vol. 9, no. 1, pp. 1–25, Dec. 2023, doi: 10.1186/S40854-
       022-00431-9/TABLES/8.
[9]    Goodfellow Ian, Bengio Yoshua, and Courville Aaron, Deep Learning, 1st ed. MIT Press, 2016.
       Accessed: Jan. 24, 2024. [Online]. Available: https://www.deeplearningbook.org/
[10]   J. Chung, C. Gulcehre, K. Cho, and Y. Bengio, “Empirical evaluation of gated recurrent neural
       networks on sequence modeling,” in NIPS 2014 Workshop on Deep Learning, December 2014,
       2014. doi: https://doi.org/10.48550/arXiv.1412.3555.
[11]   F. Hutter, H. H. Hoos, and K. Leyton-Brown, “Sequential Model-Based Optimization for
       General Algorithm Configuration,” 2011, pp. 507–523. doi: 10.1007/978-3-642-25566-
       3_40.
[12]   D. Selvamuthu, V. Kumar, and A. Mishra, “Indian stock market prediction using artificial
       neural networks on tick data,” Financial Innovation, vol. 5, no. 1, pp. 1–12, Dec. 2019, doi:
       10.1186/S40854-019-0131-7/FIGURES/5.
[13]   J. Cao, Z. Li, and J. Li, “Financial time series forecasting model based on CEEMDAN and
       LSTM,” Physica A: Statistical Mechanics and its Applications, vol. 519, pp. 127–139, Apr.
       2019, doi: 10.1016/J.PHYSA.2018.11.061.
[14]   L. Chen, Y. Chi, Y. Guan, and J. Fan, “A Hybrid Attention-Based EMD-LSTM Model for Financial
       Time Series Prediction,” 2019 2nd International Conference on Artificial Intelligence and Big
       Data, ICAIBD 2019, pp. 113–118, May 2019, doi: 10.1109/ICAIBD.2019.8837038.
[15]   J. Shen and M. O. Shafiq, “Short-term stock market price trend prediction using a
       comprehensive deep learning system,” J Big Data, vol. 7, no. 1, pp. 1–33, Dec. 2020, doi:
       10.1186/S40537-020-00333-6/TABLES/9.
[16]   C. Yang, J. Zhai, and G. Tao, “Deep Learning for Price Movement Prediction Using
       Convolutional Neural Network and Long Short-Term Memory,” Math Probl Eng, vol. 2020,
       pp. 1–13, Jul. 2020, doi: 10.1155/2020/2746845.
[17]   X. Ji, J. Wang, and Z. Yan, “A stock price prediction method based on deep learning
       technology,” International Journal of Crowd Science, vol. 5, no. 1, pp. 55–72, Apr. 2021, doi:
       10.1108/IJCS-05-2020-0012/FULL/PDF.
[18]   Y. Lin, Q. Liao, Z. Lin, B. Tan, and Y. Yu, “A novel hybrid model integrating modified ensemble
       empirical mode decomposition and LSTM neural network for multi-step precious metal
       prices prediction,” Resources Policy, vol. 78, p. 102884, Sep. 2022, doi:
       10.1016/J.RESOURPOL.2022.102884.
[19]   C. Li and G. Qian, “Stock Price Prediction Using a Frequency Decomposition Based GRU
       Transformer Neural Network,” Applied Sciences 2023, Vol. 13, Page 222, vol. 13, no. 1, p. 222,
       Dec. 2022, doi: 10.3390/APP13010222.
[20]   P. L. Seabe, C. R. B. Moutsinga, and E. Pindza, “Forecasting Cryptocurrency Prices Using
       LSTM, GRU, and Bi-Directional LSTM: A Deep Learning Approach,” Fractal and Fractional
       2023, Vol. 7, Page 203, vol. 7, no. 2, p. 203, Feb. 2023, doi:
       10.3390/FRACTALFRACT7020203.
[21]   N. E. Huang et al., “The empirical mode decomposition and the Hilbert spectrum for
       nonlinear and non-stationary time series analysis,” RSPSA, vol. 454, no. 1971, pp. 903–998,
       1998, doi: 10.1098/RSPA.1998.0193.
[22]   M. J. Zaki and W. Meira, Jr, “Data Mining and Machine Learning: Fundamental Concepts and
       Algorithms,” Data Mining and Machine Learning, Jan. 2020, doi: 10.1017/9781108564175.
[23]   D. P. Kingma and J. Ba, “Adam: A Method for Stochastic Optimization,” International
       Conference on Learning Representations, 2014.
[24]   S. Mehtab and J. Sen, “Stock Price Prediction Using CNN and LSTM-Based Deep Learning
       Models,” 2020 International Conference on Decision Aid Sciences and Application, DASA 2020,
       pp. 447–453, Nov. 2020, doi: 10.1109/DASA51403.2020.9317207.
[25]   Y. Gao, R. Wang, and E. Zhou, “Stock Prediction Based on Optimized LSTM and GRU Models,”
       Sci Program, vol. 2021, 2021, doi: 10.1155/2021/4055281.
[26]   C. Chen, L. Xue, and W. Xing, “Research on Improved GRU-Based Stock Price Prediction
       Method,” Applied Sciences 2023, Vol. 13, Page 8813, vol. 13, no. 15, p. 8813, Jul. 2023, doi:
       10.3390/APP13158813.