Expose number of bins used by the model while binning continuous features to C API

[narendramukherjee]

Hi,

I am using the sklearn api to lightgbm, and am wondering if there's a way I can get the number of bins (defined to be < max_bin) that the model creates while binning continuous features? I found the cpp code that counts up the bins (in num_bin_) here: https://github.com/Microsoft/LightGBM/blob/7a89d0054bcf0db9f96af3c53a078b6aa3152efe/src/io/bin.cpp#L207-L401 , going from #2063 , but is there a way to get this number from a trained model for each feature it binned?

Thanks in advance for any help!

[guolinke]

sorry, this api is not exposed. Exposing it is relatively easy, contribution is very welcome!

[narendramukherjee]

Thanks @guolinke - can you give me some pointers on how to go about exposing this part of the api? I can then make an appropriate PR

[guolinke]

you can add the related function in c_api.h and c_api.cpp.
like

LightGBM/src/c_api.cpp

Lines 1486 to 1492 in ceb6265

	int LGBM_DatasetGetNumData(DatasetHandle handle,
	int* out) {
	API_BEGIN();
	auto dataset = reinterpret_cast<Dataset*>(handle);
	*out = dataset->num_data();
	API_END();
	}

[StrikerRUS]

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.

[jmoralez]

Reopening since I'm working on this.

[github-actions]

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