Extract length of data in a structure

I have a structure with arrays of different size inside:

STRUC(1).meas=ones(101,2)
STRUC(2).meas=ones(34,2)
STRUC(3).meas=ones(33,2)
STRUC(4).meas=ones(101,2)

now I want to get an index, which shows me all entries, where the size of STRUC.meas is > 100:

idx=[1 4]

so that I can filter all entries of STRUC with this condition (incl. other fields) with

STRUC(idx)

As I understand structfun is only for scalar structs... is there an easy and elegant way (if possible without for-loop)?

Answer 1

[Jos (10584)]

Still no need for a conversion:

   a(1).b=ones(4,8);
   a(2).b=ones(8,1);
   a(3).b=ones(3,2);
   a(4).b=ones(7,1);

   lengths = arrayfun(@(x) size(a(x).b,1), 1:numel(a))
   keepA = a(lengths>5)

[Andrei Bobrov]

+1

Answer 2

[Jos (10584)]

No need for conversion to cell array. Use STRUCTFUN on the structure directly:

 a(1).b=ones(4,8);
 a(2).b=ones(8,1);
 a(3).b=ones(3,2);
 a(4).b=ones(7,1);
 lengths = structfun(@(x) size(x,1), a)
 keepA = a(lengths>5)

[Patrik Ek]

Sorry, this will not work on a struct array. structfun works only on scalar structs, thus the struct array need to be converted to a format matlab can handle.

[Jos (10584)]

Yes, you're right. But there is really no need for a conversion! See my 2nd answer.

Answer 3

[W. Owen Brimijoin]

If you are intent on avoiding a for-loop, then you could try converting the structure to a cell array and then using a cell function. An example would look something like this:

idx = cellfun(@length,struct2cell(STRUC(:)))>100

idx =

         1     0     0     1