[docs] clarified support of LibSVM zero-based format files (#2504)

docs/FAQ.rst

@@ -172,6 +172,11 @@ In ``LightGBM``, `we have decided to require that users specify this set directl
 
 The appropriate splitting strategy depends on the task and domain of the data, information that a modeler has but which ``LightGBM`` as a general-purpose tool does not.
 
+13. Does LightGBM support direct loading data from zero-based or one-based LibSVM format file?
+----------------------------------------------------------------------------------------------
+
+LightGBM supports loading data from zero-based LibSVM format file directly.
+
 ------
 
 R-package

docs/Parameters.rst

@@ -577,7 +577,7 @@ IO Parameters
 
 -  ``zero_as_missing`` :raw-html:`<a id="zero_as_missing" title="Permalink to this parameter" href="#zero_as_missing">&#x1F517;&#xFE0E;</a>`, default = ``false``, type = bool
 
-   -  set this to ``true`` to treat all zero as missing values (including the unshown values in libsvm/sparse matrices)
+   -  set this to ``true`` to treat all zero as missing values (including the unshown values in LibSVM / sparse matrices)
 
    -  set this to ``false`` to use ``na`` for representing missing values
 

docs/Python-Intro.rst

@@ -34,7 +34,7 @@ Data Interface
 
 The LightGBM Python module can load data from:
 
--  libsvm/tsv/csv/txt format file
+-  LibSVM (zero-based) / TSV / CSV / TXT format file
 
 -  NumPy 2D array(s), pandas DataFrame, H2O DataTable's Frame, SciPy sparse matrix
 
@@ -48,7 +48,7 @@ Many of the examples in this page use functionality from ``numpy``. To run the e
 
     import numpy as np
 
-**To load a libsvm text file or a LightGBM binary file into Dataset:**
+**To load a LibSVM (zero-based) text file or a LightGBM binary file into Dataset:**
 
 .. code:: python
 

docs/Quick-Start.rst

@@ -18,7 +18,7 @@ Follow the `Installation Guide <./Installation-Guide.rst>`__ to install LightGBM
 Training Data Format
 --------------------
 
-LightGBM supports input data files with `CSV`_, `TSV`_ and `LibSVM`_ formats.
+LightGBM supports input data files with `CSV`_, `TSV`_ and `LibSVM`_ (zero-based) formats.
 
 Files could be both with and without `headers <./Parameters.rst#header>`__.
 

include/LightGBM/config.h

@@ -551,7 +551,7 @@ struct Config {
   // desc = set this to ``false`` to disable the special handle of missing value
   bool use_missing = true;
 
-  // desc = set this to ``true`` to treat all zero as missing values (including the unshown values in libsvm/sparse matrices)
+  // desc = set this to ``true`` to treat all zero as missing values (including the unshown values in LibSVM / sparse matrices)
   // desc = set this to ``false`` to use ``na`` for representing missing values
   bool zero_as_missing = false;