Replacing a cell value in a struct

Hello,

I have a struct with 4 fields.

One field contains my conditions (3 conditions, named using strings)

Now I want to replace the strings with numbers. How is that possible? So far I could not find anything :( Is this even possible?

Help is much appreciated!

Answer 1

[Image Analyst]

This works:

% Identify what number should replace what character vector.
replacements = {'condi1', 1; 'condi2', 2; 'condi3', 3}
% Make cell array for Conditions
caConditions = {'condi1' 'condi2' 'condi3' 'condi3' 'condi1' 'condi3' 'condi2'}
% Create the whole structure array.
s = struct('subjectnumber', {1 1 1 1 1 1 1}, ...
	'condition', caConditions, ...
	'rt',{0.12 0.11 0.8 0.9 0.13 0.6 0.12}, ...
	'point',{0 40 40 40 20 20 0})
for k = 1 : numel(s)
	thisCondition = {s(k).condition}; % Character vector like 'condi1', or 'condi2', etc.
	% Compare this condition to the list of them in column 1 of replacements
	% and find out which row contains the replacement.
	[~, row] = ismember(thisCondition, replacements(:, 1));
	% Replace it with the number in column 2
	s(k).condition = replacements{row, 2};
end

[deejt]

Thank you so much! This indeed solved my problem!!!

How would I proceed, if I had so many more entries (because 7 is very easy).

But at this part for example: what if I had 24778 entries - I can't possibly type in everything manually can I?

s = struct('subjectnumber', {1 1 1 1 1 1 1}, ...
	'condition', caConditions, ...
	'rt',{0.12 0.11 0.8 0.9 0.13 0.6 0.12}, ...
	'point',{0 40 40 40 20 20 0})

[Image Analyst]

Are you saying that you could have 25 thousand different strings? If so, rather than a look up table like I used, you'd need to use something like sscanf() to parse/extract the number out of the character string.

Answer 2

[Image Analyst]

Yes. For example to set the "condition" field to the number 5, do this:

yourStruct.condition = 5;

It doesn't matter that it used to be a string.

Attach your structure in a .mat file, or give code to create it, if you still have problems.

[deejt]

thanks for the response, however, unfortunately, that's not quit it.

mydata= struct with fields:

time: [0 0 0 0 0 0 0 0 0 0]

name: 'a'

point: 3.1416

condition: 'fourth' 'fifth' 'sixth'

I do not want to change the name of the field but its corresponding values, i.e., 'fifth'to the numerical value 2.

Kind of have the feeling, that this might not be possible..

[Bob Thompson]

Image Analyst's suggestion will change the value of the field, rather than the name. mydata.condition will still be called mydata.condition, it will just simply be a numerical value, instead of a string.

Are you looking to mix class values for the different values within the condition field? i.e. change 'fifth' to 2, but keep 'fourth' and 'sixth'? That's a bit more complicated, as you will need mydata.condition to contain cell class values, but it's certainly possible.

Are you looking to do a search and replace? i.e. check all mydata.condition values for 'fifth' and replace with 2?

Or are you trying to say that there is more data within 'condition' that you want to keep 'fifth,' but the related data should be changed to 2?

[Image Analyst]

AGAIN:

Attach your structure in a .mat file, or give code to create it, if you still have problems.

I need it because I'm not sure how condition is what you showed : 3 character arrays. It can be a character matrix, a string vector, or even a cell array, but I don't know what you have or how you displayed that. Plus answer Bob's questions.

[deejt]

@Image Analyst when I tried your suggestion I received an error msg unfortunately. I attached it here, maybe I am overseeing something! (I am new to programming and just trying to figure out some basics).

"Scalar structure required for this

assignment.

Error in TutorialSession (line 4)

s.condition = 5"

Answer 3

[deejt]

Thank you guys for the effort.

@Bob Thompson Yes, I am trying to do a search/find and replace. In every cell of the field block I want to change the name that is in string to a numerical value.

condi1 should become 1, condi2 should become 2, condi3 should become 3 in every cell these string appear.

Thank you!