# Introduction by Example¶

This guide covers how to use the transformer with tabular models in your own project. We use a BertWithTabular model as an example.

For a working script see the github repository.

## How to Initialize Transformer With Tabular Models¶

The models which support tabular features are located in multimodal_transformers.model.tabular_transformers. These adapted transformer modules expect the same transformer config instances as the ones from HuggingFace. However, expect a multimodal_transformers.model.TabularConfig instance specifying the configs.

Say for example we had categorical features of dim 9 and numerical features of dim 5.

from transformers import BertConfig

from multimodal_transformers.model import BertWithTabular
from multimodal_transformers.model import TabularConfig

bert_config = BertConfig.from_pretrained('bert-base-uncased')

tabular_config = TabularConfig(
combine_feat_method='attention_on_cat_and_numerical_feats',  # change this to specify the method of combining tabular data
cat_feat_dim=9,  # need to specify this
numerical_feat_dim=5,  # need to specify this
num_labels=2,   # need to specify this, assuming our task is binary classification
use_num_bn=False,
)

bert_config.tabular_config = tabular_config

model = BertWithTabular.from_pretrained('bert-base-uncased', config=bert_config)


In fact for any HuggingFace transformer model supported in multimodal_transformers.model.tabular_transformers we can initialize it using multimodal_transformers.model.AutoModelWithTabular to leverage any community trained transformer models

from transformers import AutoConfig

from multimodal_transformers.model import AutoModelWithTabular
from multimodal_transformers.model import TabularConfig

hf_config = AutoConfig.from_pretrained('ipuneetrathore/bert-base-cased-finetuned-finBERT')
tabular_config = TabularConfig(
combine_feat_method='attention_on_cat_and_numerical_feats',  # change this to specify the method of combining tabular data
cat_feat_dim=9,  # need to specify this
numerical_feat_dim=5,  # need to specify this
num_labels=2,   # need to specify this, assuming our task is binary classification
)
hf_config.tabular_config = tabular_config

model = AutoModelWithTabular.from_pretrained('ipuneetrathore/bert-base-cased-finetuned-finBERT', config=hf_config)


## Forward Pass of Transformer With Tabular Models¶

During the forward pass we pass HuggingFace’s normal transformer inputs as well as our categorical and numerical features.

The forward pass returns

• torch.FloatTensor of shape (1,): The classification (or regression if tabular_config.num_labels==1) loss

• torch.FloatTensor of shape (batch_size, tabular_config.num_labels): The classification (or regression if tabular_config.num_labels==1) scores (before SoftMax)

• list of torch.FloatTensor The outputs of each layer of the final classification layers. The 0th index of this list is the combining module’s output

The following example shows a forward pass on two data examples

from transformers import BertTokenizer
tokenizer = BertTokenizer.from_pretrained("bert-base-cased")

text_1 = "HuggingFace is based in NYC"
text_2 = "Where is HuggingFace based?"
model_inputs = tokenizer([text_1, text_2])

# 5 numerical features
numerical_feat = torch.rand(2, 5).float()
# 9 categorical features
categorical_feat = torch.tensor([[0, 0, 0, 1, 0, 1, 0, 1, 0],
[1, 0, 0, 0, 1, 0, 1, 0, 0]]).float()
labels = torch.tensor([1, 0])

model_inputs['cat_feats'] = categorical_feat
model_inputs['num_feats'] = numerical_feat
model_inputs['labels'] = labels

loss, logits, layer_outs = model(**model_inputs)


We can also pass in the arguments explicitly

loss, logits, layer_outs = model(
model_inputs['input_ids'],
token_type_ids=model_inputs['token_type_ids'],
labels=labels,
cat_feats=categorical_feat,
numerical_feats=numerical_feat
)


## Modifications: Only One Type of Tabular Feature or No Tabular Features¶

If there are no tabular features, the models basically default to the ForSequenceClassification models from HuggingFace. We must specify combine_feat_method='text_only' in multimodal_transformers.model.TabularConfig. During the forward pass we can simply pass the text related inputs

loss, logits, layer_outs = model(
model_inputs['input_ids'],
token_type_ids=model_inputs['token_type_ids'],
labels=labels,
)


If only one of the features is available, we first must specify a combine_feat_method that supports only one type of feature available. See supported methods for more details. When initializing our tabular config we specify the dimensions of the feature we have. For example if we only have categorical features

tabular_config = TabularConfig(
combine_feat_method='attention_on_cat_and_numerical_feats',  # change this to specify the method of combining tabular data
cat_feat_dim=9,  # need to specify this
num_labels=2,   # need to specify this, assuming our task is binary classification
)


During the forward pass, we also pass only the tabular data that we have.

loss, logits, layer_outs = model(
model_inputs['input_ids'],
token_type_ids=model_inputs['token_type_ids'],
labels=labels,
cat_feats=categorical_feat,
)


## Inference¶

During inference we do not need to pass the labels and we can take the logits from the second output from the forward pass of the model.

with torch.no_grad():
_, logits, classifier_outputs = model(
model_inputs['input_ids'],
token_type_ids=model_inputs['token_type_ids'],
cat_feats=categorical_feat,
numerical_feats=numerical_feat
)