How can i access field values of a struct by indexing?
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Henning Wilhelm
am 6 Nov. 2017
Kommentiert: Walter Roberson
am 26 Jan. 2021
My struct has several fields containing a matrix. How can I get the first 100 values of each field without using a for loop.
a = b.(fieldnames(b))(1:100,:); % wont work
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Walter Roberson
am 6 Nov. 2017
a = structfun(@(F) F(1:100,:), b, 'uniform', 0)
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Rik
am 26 Jan. 2021
That is true in general. The best you can hope for is parity (given proper pre-allocation). Every function that hides a loop (cellfun, arrayfun, etc) will have an overhead. Matlab is getting better and better at for-loops.
The only exception to this rule is if you have actual array operations:
%slow:
s=0;for n=1:numel(data),s=s+data(n);end
%fast
s=sum(data);
Walter Roberson
am 26 Jan. 2021
Anonymous functions are more expensive than plain function handles such as @sin
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