I need help with the following scenario. Imagine that my original data have this format:

In this example, the values in the Feature 1, Feature 3 and Target are the same for each group. I want to split this data so I have two inputs

InputA, with only the features with the same values and grouped by group:

And InputB, with the features where the values differ inside the group:

So I ended up with InputA with 4 features and 3 rows (shape (4, 3)) and InputB with 2 features and 6 rows (shape (6, 2)).

My question is : Can I build a multi input model using tensorflow and/or keras using inputs with different numbers of columns and rows?

After splittting the target from the InputA data and splitting both inputs into train and test, I ended up with six datasets: inputA_train, inputA_test, inputB_train, inputB_test and the target (y_train and y_test).

I created the model for the InputA:

a_input = tf.keras.Input(shape=(inputA_train.shape[1]), name='a_input')
x = tf.keras.layers.Flatten()(a_input)
x = tf.keras.layers.Dense(32)(x)

And I also created the model for the InputB:

b_input = tf.keras.Input(shape=(inputB.shape[1]), name='b_input')
y = tf.keras.layers.Flatten()(b_input)
y = tf.keras.layers.Dense(64)(y)

After that I concatenate both models, build and compile the final model:

z = tf.keras.layers.Concatenate()([x, y])
z = tf.keras.layers.Dense(1, activation="sigmoid")(z)

model = tf.keras.models.Model(inputs=[a_input, b_input], outputs=z)
model.compile(loss='binary_crossentropy', optimizer='adam', metrics=['accuracy'])

Finally, I tried to fit this model:

model.fit(
    x=[inputA_train, inputB_train], 
    y=y_train,
    validation_data=([inputA_test, inputB_test], y_test),
    epochs=10,
)

If I try to fit this model using pandas dataframes I get the following error:

ValueError: Data cardinality is ambiguous:
Make sure all arrays contain the same number of samples.

Another question that I have here regarding multi-input models: Can I have only one dataset containing the target feature with a number of samples equal to only one of the inputs used by the model or each input need to have its own target dataset?

I also tried to convert the pandas dataframe into a tensorflow dataset:

inputA_train_ds = tf.data.Dataset.from_tensor_slices((inputA_train))
inputA_test_ds = tf.data.Dataset.from_tensor_slices((inputA_test))

inputB_train_ds = tf.data.Dataset.from_tensor_slices((inputB_train))
inputB_test_ds = tf.data.Dataset.from_tensor_slices((inputB_test))

I tried to fit the model again using the datasets:

model.fit(
    x=[inputA_train, inputB_train], 
    y=y_train,
    validation_data=([inputA_test, inputB_test], y_test),
    epochs=10,
)

Now I get the following error:

ValueError: Failed to find data adapter that can handle input: (<class 'list'> containing values 
of types {"<class 'tensorflow.python.data.ops.dataset_ops.TensorSliceDataset'>"}), <class 'pandas.core.series.Series'>

I want to know if it’s possible to build the model that I described here and, if it’s indeed possible, I want to know what I need to change in my code to fix these errors that I’m encountering.

Thanks in advance