Removing empty structure fields Matlab

Question

I'm facing the following problem: I have an array of structures like:

A.B(1,1).x = 'string'
A.B(1,1).y = 12
A.B(1,2).x = []
A.B(1,2).y = []
A.B(1,3).x = 'string2'
A.B(1,3).y = 4

And I would like to remove the empty 2. row from this structure, so that in the end I get fields for (1,1) and (1,3). I was trying to convert to cells, remove and then back to structure, but this way I had to retype names of fields. How is it possible to do it? Can it be done without conversion from structures?

tia!

Gunther Struyf · Accepted Answer · 2012-08-08 14:59:07Z

2

Use a loop or arrayfun to determine which array elements are empty:

empty_elems = arrayfun(@(s) isempty(s.x) & isempty(s.y),A.B)

returns: [0 1 0]

or

empty_elems = arrayfun(@(s) all(structfun(@isempty,s)), A.B);

which checks if all fields are empty (use any instead of all to check if any element is empty instead of all).

Then remove them using logical indexing:

A.B(empty_elems) = [];

Full solution to your problem in comments:

% find array elements that have all fields empty:
empty_elems = arrayfun(@(s) all(structfun(@isempty,s)), A.B);

% copy non-empty elements to a new array `C`:
C = A.B(~empty_elems);

% find elements of C that have y field >3
gt3_elems = arrayfun(@(s) s.y<3,C);

% delete those form C:
C(gt3_elems) = [];

execute this code step by step and analyze the intermediary variables to understand what's happening. It should be fairly clear.

edited Aug 8, 2012 at 14:59

answered Aug 8, 2012 at 14:04

Gunther Struyf

11.2k2 gold badges36 silver badges58 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

beginh Over a year ago

what if I had much more fields like x,y,z etc. is there an efficient way to write this condition? because for just one condition isempty(s.x) it does not remove empty fields

Gunther Struyf Over a year ago

maybe structfun is applicable...

beginh Over a year ago

actually I was thinking about the following, that I have at first A.B the whole with data. then i apply a condition for A.B.().y > 3 and if so save in a new structure, from which I got this empty A.B.(1,2) (let's say A.B.(1,2).y = 2). is there maybe a better way to avoid the empty fields in the structure at once?

Gunther Struyf Over a year ago

problem is comparing a number with an empty field will yield an empty result. I suggest first filtering the empty ones out, and then applying your condition.

beginh Over a year ago

I am not sure if I understand well, but if so, then .. empty fields are the effect of applying my condition. Before all the fields had values, and due to the fact 2<3 I got empty fields.

|

Collectives™ on Stack Overflow

Removing empty structure fields Matlab

1 Answer 1

8 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Related