error with || and && operators in a while loop

Hello!

I have written a script in matlab, using the psychophysics toolbox and I keep getting this error

"Operands to the and && operators must be convertible to logical scalar values.

Error in myscript (line 196)

                if strcmp(KbName(keyCode), 'm') || strcmp(KbName(keyCode), 'z')

This is the whole while loop in which the error occurs:

% Check the keyboard.

        while respToBeMade == true
            [keyIsDown, pressedSecs, keyCode] = KbCheck(-1);
            if keyIsDown
                if strcmp(KbName(keyCode), 'm') || strcmp(KbName(keyCode), 'z') 
                    disp(KbName(keyCode));
                    respToBeMade = false;
                    break;
                end
            end
        end

Thanks on advance for your help.

Best,

-Maria

Answer 1

[Guillaume]

I don't have the psychotoolbox, but have a look at the documentation of kbCheck.

The reason you get an error is because the keyCode it returns is either empty or more than one value.

If it can be empty, you could change your test to

if ~isempty(keyCode) && ismember(kbName(keyCode), {'m', 'z'})

If it can be more than one value then

if any(ismember(kbName(keyCode), {'m', 'z'}))

or

if all(ismember(kbName(keyCode), {'m', 'z'}))

depending on what you want to test.

Note that

if ismember(kbName(keyCode), {'m', 'z'})

is equivalent to

if strcmp(KbName(keyCode), 'm') || strcmp(KbName(keyCode), 'z')

but obviously less to type and more extensible if you want to add more accepted key codes.

[Maria K]

Thanks, I only get the error when I try to log the answers in a text file, but the 'ismember' thing might help me in the future!