How to use histcounts with struct array?

Hello,

I have a problem, I want to do this:

y = 10e-9*rand(270,1);
bins=linspace(0,10e-9,11);
[N,bincounts, binidx] = histcounts(y, bins);

So far no problem, however the value y is in my case the z-coordinate of a struct:

particle(i).coord(1:3);

I can get with a loop these values of particle(i).coord(3) in an array that I can use for input of histcounts.

But for performance reason I want direct access to the structure? Is this possible? I Googled and I found:

<https://nl.mathworks.com/help/matlab/matlab_prog/access-data-in-a-structure-array.html >

"You can index into part of a field only when you refer to a single element of a structure array. MATLAB® does not support statements such as S(1:2).X(1:50,1:80), which attempts to index into a field for multiple elements of the structure."

So I hope someone can help me.

Thanks for your time.

Regards,

Olaf

This is my first mail in this forum. However, I've read and learned a lot from it :)

[Image Analyst]

I fixed your formatting. You can learn how to do it yourself here http://www.mathworks.com/matlabcentral/answers/13205#answer_18099

I assume you wanted to know how to vectorize and use handy built in functions like Jos showed you below, rather than for performance reasons. For a microscopic array with only 270 elements, no performance difference will be human noticeable at all between using a for loop and using arrayfun().

Answer 1

[Jos (10584)]

Welcome to the forum!

You can use a loop or arrayfun to extract the scalar value, like:

y = arrayfun(@(k) particle(k).coord(3), 1:numel(particle)) ;

[Olaf van Buul]

Hello Jos,

I coded

tic;
yyy = arrayfun(@(k) particle(k).coord(3), 1:numel(particle)) ; 
toc;

tic;
for i=1:TOTAL_NUMBERS_ATOMS
    y(i) = particle(i).coord(3);
end;
toc;

Elapsed time is 0.002761 seconds.
Elapsed time is 0.000274 seconds.

I was not expecting a difference of factor 10. As ImageAnalyst stated no performance difference will be human noticeable between them is true, except that I will be doing this at least 100000 times in my code.

Thanks both of you for your time.

Regards,

Olaf