Empty all the fields of a structure array in Matlab

Question

For simplicity's sake let us stick to this official Matlab example.

I run the following code, and a structure with three fields is created.

patient.name = 'John Doe';
patient.billing = 127.00;
patient.test = [79, 75, 73; 180, 178, 177.5; 220, 210, 205];

Then, in order to create a structure array, I simply have to do the following.

patient(2).name = 'Ann Lane';
patient(2).billing = 28.50;
patient(2).test = [68, 70, 68; 118, 118, 119; 172, 170, 169];

At this point I have a structure array that is clearly represented by this picture: enter image description here

Here comes the question: how can I empty all the fields of the structure patient(2)?

Ideally (forgive the abuse of notation) I would like to do something like patient(2).* = {}.

Calling the fields one by one is not an option because in my actual code I have a lot of fields, neither I can convert the structure to a cell.

Thanks in advance!

@Ander Biguri Thank you so much for adding the image to the question, I did not have the necessary reputation at the time I posted :) — wizclown
– wizclown, Commented Jul 18, 2014 at 15:25

user2271770 · Accepted Answer · 2014-07-18 15:55:55Z

3

If this operation is frequent, a good idea would be to prepare an EMPTY_PATIENT:

EMPTY_PATIENT = struct( ...
   'name', {},          ...
   'billing', {},       ...
   'test', {}           ...
);

then use the simple assignment (which is very fast) to empty the position:

patient(2) = EMPTY_PATIENT;

answered Jul 18, 2014 at 15:55

user2271770

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2 Comments

wizclown Over a year ago

For sure this is the safest and fastest way to go, using a foo empty structure! Thank you CST :)

sco1 Over a year ago

As a general remark: if there is only one level and you have a lot of fields to populate, you can get away with entering one fieldname and MATLAB will populate the remainder. For example: patient(end+1).name = []; empty_patient = patient(end); patient(end) = []; Saves some typing

sco1 · Accepted Answer · 2014-07-18 15:46:57Z

1

I'm sure there's a clever way to do it without the loop but this works fine.

fieldstoclear = fieldnames(patient(2));

for ii = 1:length(fieldstoclear)
    patient(2).(fieldstoclear{ii}) = [];
end

edit: forgot about structfun:

patient(2) = structfun(@(x) [], patient(2), 'UniformOutput',false)

Note: Neither method will preserve nested structures.

edited Jul 18, 2014 at 15:46

answered Jul 18, 2014 at 15:31

sco1

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1 Comment

wizclown Over a year ago

Thank you excaza, this goes in the right direction. Anyway the nested structures are of importance in this case, so I cannot really accept this as an answer! But again it really is a step forward, thank you!

ewz · Accepted Answer · 2014-07-18 15:25:52Z

0

 patient(2) = [];

Might be what you are looking for. This will eliminate that element from the structure.

answered Jul 18, 2014 at 15:25

ewz

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1 Comment

wizclown Over a year ago

Thank you for your answer, but I actually need to keep the element because the size of the array plays a role in my code. I expressly need to empty its field, not to delete it.

cmoxiv · Accepted Answer · 2014-07-18 15:59:30Z

0

This should be a generic solution for any number of fields.

fields=fieldnames(patient);
patient(2)=cell2struct(cell(length(fields), 1), fields);

answered Jul 18, 2014 at 15:59

cmoxiv

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