The Super Characters method addresses sentiment analysis problems by first converting the input text into images and then applying 2D-CNN models to classify the sentiment. It achieves state of the art performance on many benchmark datasets. However, it is not as straightforward to apply in Latin languages as in Asian languages. Because the 2D-CNN model is designed to recognize two-dimensional images, it is better if the inputs are in the form of glyphs. In this paper, we propose SEW (Squared English Word) method generating a squared glyph for each English word by drawing Super Characters images of each English word at the alphabet level, combining the squared glyph together into a whole Super Characters image at the sentence level, and then applying the CNN model to classify the sentiment within the sentence. We applied the SEW method to Wikipedia dataset and obtained a 2.1% accuracy gain compared to the original Super Characters method. In this CL-Aff shared task on the HappyDB dataset, we applied Super Characters with SEW method and obtained 86.9% accuracy for agency classification and 85.8% for social accuracy classification on the validation set based on 80%:20% random split on the given labeled dataset.
The need to classify sentiment arises in many different problems in customer
related marketing fields. Super Characters [
(a) Raw Super Characters method for English sentence on alphabet level.
(b) Raw Super Characters method for English sentence on alphabet level with changing line to avoid breaking words. (c) Squared English Word (SEW) method with 6x6 words per image.
(d) Squared English Word method with attention on the first four words. (e) Squared English Word method using both happy moment text and profiles information, age 36, country India (IND), married (m), male (m).
(f) Squared English Word method using happy moment text and attended profile, age 36, country India (IND), married (m), male (m).
Fig. 1. Demonstrations of raw Super Characters method and Squared English Word
method. We use the same example input to illustrate our idea. The raw text input
sentence is: “Last month my son got his first trophy in the tennis match and i was very
happy and he was very excited to see me his trophy and i took him out for dinner and
spend the evening happily with him.”
which collects Japanese shopping reviews evenly split into positive and
negative, Super Characters obtained a 94.85% accuracy, compared to the 94.55%
accuracy of the best existing method. Yet on another dataset of 11st Binary[
However, there are a few challenges of using the Super Characters method
for Latin language inputs. First, the Super Characters method can be directly
applied for Asian languages with glyph characters, such as Chinese, Japanese,
and Korean, but not so in such a straightforward fashion to Latin languages such
as English. This is because the CNN model connected to the super characters
images are designed to recognize two-dimensional images better in the form of a
glyph in a square form. Languages like Chinese build their language system upon
logograms, which are symbols or characters that serve to represent a phrase or
word. If we directly apply Super Characters method to represent sentences in
the English language, the Super Characters image is shown as in Figure 1a. Or,
as shown in Figure 1b if we try to avoid breaking the words and changing lines
because a word is divided between two lines, it will become harder for the CNN
model to recognize. In addition, Attention models have succeeded in various
fields [
This paper borrows several ideas from both Super Characters and attention. For the first challenge, we convert each English word to a glyph, such that each word only occupies the pixels within a designated squared area. The resulting algorithm is named Squared English Word (SEW) as shown in Figure 1c. For the second challenge, we add the attention scheme in the first step of Super Characters method, i.e. during the process of Super Characters image generation. In the original Super Characters method, all the text drawn on the image are given the same size, or given the same degree of attention when it is fed into the CNN model connected to it. We add the attention scheme by allocating larger spaces for important words, e.g. those in beginning of each sentence. SEW with attention as shown in Figure 1d. We will describe the details on how to generate these images in the next section.
The CL-AFF Shared Task[
The original Super Characters method works well if the character in that
language is a glyph, and Asian characters in Chinese, Japanese, and Korean are
written in a square form. In this work, we extend the original idea of Super
Characters [
Input: text input: a string of English words Output: Sentiment Classification Result Initialization: start a blank image and set the font to draw Super Characters with, set a cut-length of the words, set counter=0, set current word=the first word in the text input, set the current word location for the current word which is a square area, and get the current word area as the area of pixels for current word location; while not at end of the input text and counter<cut-length do get the current word, set current alphabet=the first alphabet in the current word; get current word length, set location stepsize=sqrt(alphabet area) where alphabet area is current word area divided by current word length, and set the current alphabet location for current alphabet at the top-left of the squared area of the current word; while not at end of the current word do draw the current alphabet at current alphabet location; move to the next alphabet and update current alphabet; update current alphabet location by moving one location stepsize, or change line if necessary; end move to the next word; counter+=1; end Feed into CNN models, such as ResNet-50, and etc.; return Sentiment Classification Result;
Algorithm 1: Super Characters with SEW
The proposed SEW method has shown accuracy improvement on DBpedia
dataset provided in [
SC[
Accuracy 96.2% 98.3%
Compared to the original Super Characters method, SEW encapsulates one English word per square, rather than one English letter per square. The first word in the sentence goes in the top left square, and the succeeding words follow sequentially from left to right, proceeding onto the next row if necessary. Any remaining space is left empty, as a blank square.
In Figure 1c, the input image consisted of 6x6 squares, and the SEW Super Characters image is generated by only utilizing the happy moment text information. To distinguish from the other approaches below, we call this the SEW-text-only approach.
In Figure 1d, we also introduced an attention-based approach to make our model focus on particular important words or phrases within the input, such as, the first four words of the sentence. By allocating larger sized squares for the Super Characters that would hold certain English words, the convolutional layers within our model naturally dedicate greater emphasis on such words. This is common in the real world when we see signs and emphasized portion is enlarged to take attention as seen in Figure 2. Similarly, people pay more attention to headlines than regular text in newspapers.
(a) Street Sign for “East Main Street”.
(b) Street Sign for “Speed Limit 55” mph.
We call the approach in Figure 1d as SEW-text-only-Attention-Four-words, which applies the attention-based mechanism with an 8x8 input image with text only information in the happy moment. We chose to teach the network to pay particular attention to the first four words of a sentence, to see if the first four words have a large impact on the overall meaning of the sentence. With this specific implementation of the attention mechanism, we made the first four words two times the size of the rest of the words in the sentence, and positioned it on the center of the image. The regularly sized sentence flows as before, starting at the leftmost square of a row, continuing rightward on all possible places that can contain a squared English word until it hits the rightmost side of the row, then proceeding onto following rows.
In Figure 1e, we also use the profile features and happy moment text together. We set the profile features in Figure 1e as the same size as the happy moment text information. Therefore, the resulting image is a combination of raw text input of happy moment and user-provided profile information. We call this approach as SEW-text-only-and-Profile-Features.
In Figure 1f, similarly, we use both the user profile information and happy
moment into the Super Characters image. And we also utilize attention scheme for
the user profile information. We call this approach as
SEW-text-only-AttentionProfile-Features. By using XGBoost [
CL-AFF Shared Task One We focused on the above mentioned six approaches as illustrated in Figure 1 for training 2D-CNN models that could discern the agency and social tags of a given happy moment.
For each approach detailed, we trained models by labeling the images with respect to social and agency values. Two separate datasets were created for the training of two different models.
We randomly split the given labeled data into train and test at a ratio of 80%:20%. The histogram of word length distribution is given in Figure 3a for CL-AFF Train dataset, and Figure 3b for CL-AFF Test dataset.
The statistics of training and testing data set are given in Table 2.
Based on the statistics above, we set the cutlength at 36 for SEW-text-only as in Figure 1c. For the 1.39% of the sentences in the labeled data that contained more than 36 words, the 37th word and onwards were not included in the input image. In the shared task 170k test data set, 1.91% were not included. (a) Histogram of CL-AFF Train Dataset.
(b) Histogram of CL-AFF Test
Dataset.
For the attention method, we predefine an 8x8 two-dimensional array to act as the blueprint for the image inputs. There are 0s on all locations that are not designated for the special attended words, to indicate the positions allocated for such words. Of the space reserved for the attended words, all the values are -1 except for the top left box, which is of value 1. Then, we will iterate through every square on the input image. If the corresponding value on the blueprint array based on the given indices a 0, we will draw the next English word in the input sentence using the SEW method. Should the value be 1, we will draw the SEW words in a larger font, and if it is -1, we will skip this iteration of the loop.
Table 3 shows our result based on a split of labeled data into 80%:20% for
training and validation. The 2D-CNN model used are all SE-Net-154 [
Approaches
Raw Super Characters method Raw Super Characters method change line
SEW-text-only SEW-text-only-Attention-Four-words
SEW-text-only-and-Profile-Features SEW-text-only-Attention-Profile-Features
Comparing SEW-text-only with the raw Super Characters method with line change, we see a little accuracy improvement on agency prediction, from 85.7% to 85.9%. Social accuracy improved from 82.5% to 83.3% compared with raw Super Characters method without line change, although there is no improvement if comparing SEW-text-only to the raw Super Characters with line change. Although we did not see significant accuracy improvement by using SEW method in this data set, it did help improve accuracy by 2.1% for the Wikipedia dataset as shown in Table 1. The main reason for no significant accuracy improvement on this CL-Aff shared task data, is because the data size is not big enough. The CL-Aff data only has a total of 10,560 training samples for different categories, whereas the Wikipedia data set has 560,000 samples for training. Since the generated SEW Super Characters images are fed into CNN models to train, significant accuracy improvement will be observed for large data set because larger data sets help train better CNN models.
For SEW-text-only and SEW-text-only-Attention-Four-words, we see 0.1% accuracy gain on agency label prediction by using attention in this data set, and we see no improvement for social prediction. Using other words to focus instead of using only the first four words, may further improve the accuracy. For example, we can use third party tools to extract keywords related to social or agency, then emphasize these words by enlarging them in the SEW image. Also, for a person’s profile information, like age, country, marriage, and gender, the approach of SEW-text-only-Attention-Profile-Features embed them in the attention area, e.g. put the gender, marriage and etc. information in the attention area.
The significant accuracy improvement for social prediction occurs when we add profile features into the SEW Super Characters image, which jumps from 83.3% to 85.6%. And the agency prediction accuracy also improves from 86.00% to 86.3%. After we further put these profile features into attention, it improves accuracy for both Agency and Social predictions. SEW-text-only-AttentionProfile-Features approach gives the best accuracy of 86.9% for agency prediction, and also the best accuracy of 85.8% for social prediction. 4
This paper borrows several ideas from Super Characters and attention, and we created a squared glyph for each English word. This Squared English Word (SEW) method can be trivially applied to other Latin languages. We apply SEW to this CL-Aff dataset, with user profile information and attention scheme added, we achieved 86.9% accuracy for agency prediction and 85.8% accuracy for social prediction on the given labeled dataset with a split of 80%:20% for training and testing. Pretrained model on large dataset could further improve the accuracy performance by finetuning the CNN models with the relatively small dataset given in this shared task.