Question

我需要你帮助解决下列问题。 Column1显示了一种按分类的分类。第2栏中的任何非南值都应列入配对组(Col1)。

mat = [ ...
        1  nan 
        1  0.1
        1  nan
        1  nan
        2  nan
        2  nan
        2  nan
        3  0.5
        4  nan
        4  nan
        4  nan
        5  0.2
        5  nan ] ;

ans = [ ...
        1  0.1 
        1  0.1
        1  0.1
        1  0.1
        2  nan
        2  nan
        2  nan
        3  0.5
        4  nan
        4  nan
        4  nan
        5  0.2
        5  0.2 ] ;

请建议采用病媒化的办法。数据是巨大的,而且已经投入到一旁。在一个群体内(按专题)永远不会有多种非南价值(栏2)。感谢!

Answer 1

利用实现以下目标:

values = accumarray(mat(:,1),mat(:,2),[],@min);
mat(:,2) = values(mat(:,1));

I use the function MIN here for convenience, since it will return the non-NaN value if there is one, or NaN if that s all there is. It s simpler than the logic involved in checking for any non-NaN values using, say, the function ISNAN. You could actually use the function MAX as well, since it behaves the same way in this case.

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