Variable passed through function doesn't work

Hello all,

I have a function where I am passing three different behaviors (drug, before drug, after drug).

function defining_parsing(subj, path, data_type, behavior)
%% loading data
all_folders = dir(fullfile(path, subj, '/dir/')); % loading all the dir folders 

% Define the regular expressions for each behavior and ROI

    if behavior == 'drug'
        expression_behavior = [data_type, '.*', '(s2|s4|s6|s3)', '.*'];
    elseif behavior == 'before drug'
        expression_behavior = [data_type, '.*', '(w3|w2|w4|w|WA)', '.*'];
    elseif behavior == 'after drug'
        expression_behavior = [data_type, '.*', '(EO)', '.*'];
    end
end 

When I pass the variable outside of the function for the above I get the following error:

Arrays have incompatible sizes for this operation.

Error in defining_parsing (line 20)
    if behavior == 'drug'

When I pass the the variable for behavior within the function, I do not get the error:

function defining_parsing(subj, path, data_type, roi, behavior)
%% 
behavior = 'drug'

%% loading data
all_folders = dir(fullfile(path, subj, '/dir/')); % loading all the dir folders 

% Define the regular expressions for each behavior and ROI

    if behavior == 'drug'
        expression_behavior = [data_type, '.*', '(s2|s4|)', '.*'];
    elseif behavior == 'before drug'
        expression_behavior = [data_type, '.*', '(w3|w2|)', '.*'];
    elseif behavior == 'after drug'
        expression_behavior = [data_type, '.*', '(EO)', '.*'];
    end
end 

I have tried the following:

1) making sure that both the variable input to the function and the variable input with the function are the same (they are both char)

if ~ischar(behavior)
    behavior = num2str(behavior);
end

2) making sure that there are no typos.

Do you have any suggestions? Thanks so much!

[nines]

I am calling the function:

behavior = 'drug'
data_type = 'intervetion'
for i = 1:length(subjs)
    subj = subjs{i}
    defining_parsing(subj, path, data_type, roi, behavior)
end

[Torsten]

function defining_parsing(subj, path, data_type, behavior)
function defining_parsing(subj, path, data_type, roi, behavior)

Do you see the difference in the list of input arguments ?

[Jan]

@nines: A note: Do not call a variable "path", because this is an important built-in function. Shadowing it by a variable can cause very strange effects during debugging.

[nines]

Thank you!

Unfortunately it was not a function list problem -- that was a typo in my question/answer. I have switched to the switch function which solved the problem!

[nines]

final thing: how do i accept an answer? the accept button isn't coming up next to any of your names!

[Fangjun Jiang]

I moved the comment by @Dyuman Joshi to an Answer. You can accept it now.

Answer 1

[Dyuman Joshi]

How are you calling the function?

Also, Use strcmp or isequal to compare strings

behavior = 'drug'

behavior = 'drug'

isequal(behavior,'drug')

ans = logical
   1

strcmp(behavior,'drug')

ans = logical
   1

You can also use switch here instead of if-else

switch behavior
    case 'drug'
        disp('1')
    case 'before drug'
        disp('2')
    case 'after drug'
        disp('3')
end

1

[Fangjun Jiang]

This explains the root cause of the error message in the OP's question. When variable "behavior" takes the value of 'before drug' and it is compared to 'drug' in the If statement.

behavior='before drug';
behavior=='drug'

Arrays have incompatible sizes for this operation.