fix interpolation documentation

[fgallardo-mpie]

Overview

Change documentation of interpolation to correctly describe the method for getting points and the method for weighing those points.

Resolves Issue #1336

Details

new description is

    n_points : int, optional
        If given, specifies the number of the closest points used to form
        the interpolation basis. This will invalidate the radius argument
        in favor of an N closest points approach. This typically has poorer
        results.

[codecov]

Codecov Report

Merging #1346 (7ab4bbb) into master (a4f148d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1346   +/-   ##
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  Coverage   90.01%   90.01%           
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  Files          56       56           
  Lines       12188    12188           
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  Hits        10971    10971           
  Misses       1217     1217           

[GuillaumeFavelier]

Thank you @fgallardo-mpie !