How to gracefully truncate a matrix of unknown dimensions?

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Disciple of the Forbidden Spell
评论： Bruno Luong 2019-7-14
Suppose here comes a
function Truncated=MatrixTruncate(Input,Dimension,a,b)
Input is a matrix, whose dimension is unknown and depends on the caller. This function will truncate the matrix along the dimension Dimension, from index a to b. Now I use eval to generate code at runtime:
Truncated=eval(['Input(' repmat(':,',1,Dimension-1) num2str(a) ':' num2str(b) repmat(',:',1,ndims(Input)-Dimension) ')']);
Personally I feel the code somewhat unnatural, though it did work. Are there any more graceful solutions?

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回答（1 个）

Bruno Luong
Bruno Luong 2019-7-13
编辑：Bruno Luong 2019-7-13
Input = rand(3,4,5)
Dimension = 2;
a=2; b=4;
commaidx = cell(size(size(Input)));
commaidx(:) = {':'};
commaidx{Dimension} = a:b;
Truncated = Input(commaidx{:})
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Tmfu Vh
Tmfu Vh 2019-7-14
Splendid solution. What if I want to use the "end" index here?
commaidx{Dimension} = a:end;
This code is not allowed.
Bruno Luong
Bruno Luong 2019-7-14
No you can't use 'end' in commalist, you have to replace it with
size(Input,Dimension)

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