Index each row of one matrix applying an operator/function to the second matrix, then concatenate all the results.

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Joshua Murray 2020-7-25

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评论： Joshua Murray 2020-7-27

I'm fairly new to Matlab. I've got the following code where I'm indexing each row of 'a' and adding it to matrix b. Then I concatenate the resultant values:

a = [0 0;100 100];
b = [1 1; 0 0];
c = a(1)+b;
d = a(2)+b;
e = [c;d];
%   the result looks like this (which is the correct result I want):
e =
     1     1
     0     0
   101   101
   100   100
%   Obviously if I try something like this is doesn't work as the matrix dimensions are different:
%   e= a(:) + b

What is the best way to do this so that the concatenating and indexing happens automatically? Should I try and figure out a for loop for every row of matrix 'a' or am I missing an easy function or trick here?

The background to why I'm asking is that I've got two much larger matricies that I have to apply something similar: indexing each row of the first matrix and applying an operator/function to the second matrix with the final matrix being a 'concatenation' of the results. I'm hoping if I can figure it for this simple problem as shown above I can apply similar principals to a large dataset.

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Answer 1

madhan ravi 2020-7-25

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 z = reshape(a(1:2),1,1,[]) + b;
 z1 = squeeze(num2cell(z,[1,2]));
 Wanted = cat(1, z1{:})

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Joshua Murray 2020-7-26

Thanks for getting me on the right track.

If I wanted to add column 2 of matrix 'a', how would I do this? For example:

% If I changed the second row of 'a' to something like this:
a = [0 0.1;100 100.1];
b = [1 1; 0 0];
 z = reshape(a(1:2),1,1,[]) + b;
 z1 = squeeze(num2cell(z,[1,2]));
 Wanted = cat(1, z1{:})

How do I get the reshape to command to apply to different rows of a (and all columns), as at the moment it only does it for column 1. I've tried changing a few values around in the reshape but I can't figure out how to apply it to different columns.

Joshua Murray 2020-7-27