How can i access field values of a struct by indexing?

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

[Rik]

Playing around with struct2cell or struct2table could probably solve this.

Answer 1

[Walter Roberson]

a = structfun(@(F) F(1:100,:), b, 'uniform', 0)

[Henning Wilhelm]

thank you

[Cris Luengo]

The funny thing is that this is slower than an explicit loop.

[Rik]

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]

Anonymous functions are more expensive than plain function handles such as @sin