(HELP) Assign char values from a structure to a double column vector

Hi, everyone! :)

I hope you all are doing well.

I wanted to ask for help, since I am struggling a bit with a for loop.

I have this for loop:

AllEvents=[];

AllEvents=zeros(length(EEG.event),1);

for i=1:length(EEG.event)

AllEvents(i,1)=EEG.event(i).type;

end

However, every time I try to run it, I get the following error:

Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-3.

The values of the variables (and/or structures, sorry I am a bit inexperienced) are:

1. AllEvents = 1244x1 double
2. EEG.event = 1 x 2444 struct array with fields: type, edftype, latency, urevent
3. i (before running the loop) = 1x1244 double
4. Mango (extra variable that I used to see the size of the EEG.event(i).type) = 1x3 char.

So far, I think the purpose of the loop is to assign the values of the EEG.event(i).type to the all events column vector, however I think it is affecting that EEG.event is a structure and the "type" field contains characters (they look like strings).

I was wondering, and I'd be truly grateful if someone could guide me with this (please).

Thank you for everything in advance.

Answer 1

[Madhav Thakker]

Hi Ana,

The error message clearly says the problem - Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-3.

AllEvents(i,1) is of size 1-by-1 and EEG.event(i).type is of size 1-by-3.

AllEvents(i,1)=EEG.event(i).type;

Can you try with something like this -

AllEvents=[];
AllEvents=char(length(EEG.event),3); % Changed the type and size so that each row is char array of size 1-by-3
for i=1:length(EEG.event)
    AllEvents(i)=EEG.event(i).type; % assigning the type value to each row
end

[Stephen23]

AllEvents(i,:) = EEG.event(i).type;
%         ^^^ Correct indexing for assigning the 1x3 char vector to each row.

But this will fail as soon as you have a <type> character vector with two, four, five, or greater number of characters. I.e. this answer is not robust. If you want to write robust code, either use a cell array or a string array.

[Ana Maldonado Gómez]

Thank you so much! :)