Parsing Utilities

Overview

Parsing utilities are a set of functions that helps generate parsing spec for tf$parse_example to be used with estimators. If users keep data in tf$Example format, they need to call tf$parse_example with a proper feature spec. There are two main things that these utility functions help:

  • Users need to combine parsing spec of features with labels and weights (if any) since they are all parsed from same tf$Example instance. The utility functions combine these specs.

  • It is difficult to map expected label by a estimator such as dnn_classifier to corresponding tf$parse_example spec. The utility functions encode it by getting related information from users (key, dtype).

Example usage with a classifier

Firstly, define features transformations and initiailize your classifier similar to the following:

Next, create the parsing configuration for tf$parse_example using classifier_parse_example_spec and the feature columns fcs we have just defined:

This label configuration tells the classifier the following:

  • weights are retrieved with key ‘example-weight’
  • label is string and can be one of the following c('photos', 'keep', ...)
  • integer id for label ‘photos’ is 0, ‘keep’ is 1, etc

Then define your input function with the help of read_batch_features that reads the batches of features from files in tf$Example format with the parsing configuration parsing_spec we just defined:

Finally we can train the model using the training input function parsed by classifier_parse_example_spec: