Store sets of values as indices in a matrix?

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BOB 2018-9-10

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评论： BOB 2018-9-10

Hi,

I have a function which produces a set of horizontal and vertical graph axes intercepts. There are 120 sets of these intercepts:

for Z = 1:120

hrz = hix(x(:,Z),mb(:,Z))'; %[X Y] Matrix of horizontal intercepts

vrt = vix(y(:,Z),mb(:,Z))'; %[X Y] Matrix of vertical intercepts

end

I want to store each of these sets of intercepts in a matrix, i.e. I want to be able to call the second set of intercepts by simply calling matrix(2).

Is anyone aware of a way to achieve this?

Thanks

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Guillaume 2018-9-10

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I'm assuming that hix and vix are functions, and I'm assuming that for each pair of vector input, they each return a vector of the same size as the input. In which case,

hrz = zeros(size(x));   %predeclare output matrix
vrt = zeros(size(x));
for Z = 1:120
   hrz(:, Z) = hix(x(:, Z), mb(:, Z));
   vrt(:, Z) = vix(y(:, Z), mb(:, Z));
end

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Guillaume 2018-9-10

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store the different length vector of each iteration of the loop in a single matrix.

Ah! That needed explaining in the question. By definition, a matrix has the same number of rows/columns for each column/row. So you can't store results of varying length in a matrix unless you pad the shorter ones (which is rarely a good approach).

You can store the results in a cell array though:

hrz = cell(1, size(x, 2));   %preallocate output
vrt = cell(1, size(x, 2));  
for Z = 1:size(x, 2)   %better not to hardcode the size
  hrz{Z} = hix(x(:, Z), mb(:, Z));
  vrt{Z} = vix(y(:, Z), mb(:, Z));
end