matrix indexing and for loops
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Hi I am still learning the ropes with Matlab and have another problem I am not sure how to get round.
I have a matrix Z which is 12x65044 and I would like to peform an operation on each individual column of the matrix. How can I do this automatically?
Perhaps something along the lines of for: Z columns(1:65044) ... perform desired function ... and then store the output vector from each function into one new matrix say Z2???
Thanks for help
댓글 수: 4
Sean de Wolski
2011년 7월 19일
@scour_man: Not being familiar with ARMASA, I have no idea.
@Jan: I was wondering if the function was numerical - we could then probably do it with a convolution.
채택된 답변
Andrei Bobrov
2011년 7월 19일
1. Loop
Z2 = zeros(size(Z));
for j1 = 1:size(Z,2)
Z2(:,j1) = fun(Z(:,i1)); % ... perform desired function 'fun'...
end
2. Use 'arrayfun'
Z2 = cell2mat(arrayfun(@(i1)fun(Z(:,i1)),1:size(Z,2),'un',0));
3. In some cases, you can use function 'bsxfun'.
ADD if the lengths of the vectors 'pred' may be different
1.
n = size(Z,2);
pred = cell(1,n);
covpred = pred;
for j1 = 1:n
[pred{j1}, covpred{j1}] = arma2pred(a,b,Z(:,j1),Lpred);
end
2.
[pred,covpred] = arrayfun(@(i1)arma2pred(a,b,Z(:,i1),Lpred),1:size(Z,2),'un',0));
댓글 수: 10
Andrei Bobrov
2011년 7월 21일
%so
a = cell(1,size(Z,2));
b = a;
Z2=a;
for j1=1:size(Z,2),
[a{j1} b{j1}]=armasel(Z(:,j1));
Z2{j1}=arma2pred(a{j1},b{j1},Z(:,j1),3);
end
%if the values of 'a' and 'b' are needed in the future
% if not, then
Z2= cell(1,size(Z,2));
for j1=1:size(Z,2),
[a, b]=armasel(Z(:,j1));
Z2{j1}=arma2pred(a,b,Z(:,j1),3);
end
추가 답변 (1개)
Jan
2011년 7월 20일
Usually error messages do not tell only the reason of an error, but also the location. And without knowing in which line the error appears, it is impossible to fix it. Without the location, an error message is not "complete".
A more direct solution of your problem would be to use the debugger to let Matlab stop, when the error appears:
dbstop if error
Then inspect the contents of the used variables in the command window or workspace browser. Then you will find out, that the dimension of the lefthand side and the righthand side of an assignment do not match. E.g. "Z2(:, j1)" is a vector, but arma2pred replies an array of a different size, e.g. empty, or matrix.
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