[R-package] lgb.convert() functions should convert columns of type 'logical'

[jameslamb]

Summary

lgb.convert() and lgb.convert_with_rules() should convert columns of type "logical" to type "integer".

Motivation

The R package currently exports two functions that can be used to convert tabular datasets into model-ready form:

• lgb.convert(): converts columns of type "character" and "factor" to "integer"
• lgb.convert_with_rules(): similar to lgb.convert(), but returns a set of "rules" describing how non-numeric values were mapped to integer values. Also allows for user-provided rules, useful for cases where you want to be sure the encoding is the same on multiple datasets (e.g. training, test, and validation datasets)

These functions are intended to make it easier to create a model-ready dataset (all numeric or all integer). The fact that they do not convert columns of type "logical" means that they don't cover a very common case...converting TRUE/FALSE to 1/0.

[jameslamb]

Closed in favor of being in #2302. We decided to keep all feature requests in one place.

Welcome to contribute this feature! Please re-open this issue (or post a comment if you are not a topic starter) if you are actively working on implementing this feature.

[jameslamb]

Just updated the title and description now that #3095 has been merged.

[jameslamb]

oh this one can stay closed @guolinke . I fixed this in #3269