I am not sure. I would recommend contacting support and reporting the behavior as a bug, which it seems like to me. But if I heard a reason that made sense, I might be swayed the other way.

–Loren

I get you on how struct array references like, temp(3:5).A, return coma lists… and, like you, don’t get the various confusions this seems to cause.

But I’m trying to understand an inconsistency (BUG?) in this behavior:

[temp(false)] = nan or [temp(4:3)] = nan

correctly, does nothing when temp is a regular array, BUT when temp is a structure containing a field “A”:

[temp(false).A] = nan or [temp(4:3).A] = nan

(Which looks look me like an IDENTICAL case given, the comma list interpretation)

gives an error about “too many elements” on the right side.

Is there a rational reason for this inconsistency that you can help me follow… or is it a BUG? It certainly complicates code to special-handle the null case.

Or, am I missing a shortcut there?

Thanks,
Darin

What code have you tried?

–Loren

A = [1 2 3; 1 2 4]

f(1).h = [1 2 5; 2 5 6; 1 2 3; 3 5 6]
f(2).h = [1 2 6; 3 5 6; 1 5 3; 3 5 6]
f(3).h = [1 2 4; 3 4 5; 1 1 3; 3 4 6]

[m,n] = arrayfun(@(x)find(x.h==A),f,'uniformoutput',false)

Can you tell me how to use the arrayfun to locate values that match entire rows in data.

i.e.

If I do this, then I get….
??? Error using ==> eq
Matrix dimensions must agree.

Error in ==> @(x)find(x.h==A)

Thanks,

Anna

Thanks for sharing your thoughts. I have made sure they got into the bug/enhancement list.

–Loren

struct arrays seem very unwieldy, they are hard to create via preallocation, and seem impossible to merge without looping, e.g. if you have a struct array O where O(i) is combination of the two structs a and b, then there is little hope of creating O(i) = mergestruct(a,b) (substitute for mergestruct your favourite vertcat function for structs here).

It would be great if mathworks provided some more tools for struct arrays, a separate class name, detection via is* functions, and vertcat methods, easier syntax for creating (preallocation especially), etc.

Best, HH

How large is f? I wonder if the code would be clearer if you wrote the for-loop.

One way is to convert the struct to a cell and work on each cell. Then convert back to a struct. Not sure this is worth the effort however.

Others?
–loren

I am beginning to learn Matlab and I have a question related to this post. Using your example, if i wanted to, first, find certain values in a struct and then replace them by another value, say 0. So the first thing would be like this:

f(1).h = [1 2 3 4];
f(2).h = [5 6 3 8];
[m,n] = arrayfun(@(x)find(x.h==3),f,'uniformoutput',false)

Now that i have the indexes, how can I replace those “3″ by, for example, 0? I mean without using loops. Thanks a lot in advance.

struct2cell should get you part of the way there – but not the data not arranged as a struct per se. You can use a for loop. Or cellfun (which effectively has a loop inside it).

–Loren