Error when If statement is not true

Hello,

I have a user supplying a 'Yes' or 'No' input to a question. I want to use the response to determine if plots are created or not. If I select 'Yes', the code runs fine. However, if I select 'No', I get this error: Error in PostProcessing_filetest (line 118) , if answer == 'Yes'. Why won't Matlab go to the else statement if the if-statement is not true? Can someone help point out my error? Below is a portion of my code. The variables in the if-portion of the code are defined before-hand. Thank you!

....

quest = 'Do you want another set of maps?';

answer = questdlg(quest);

if answer == 'Yes'

    strm1a = 'What is the map height (pixels)?';
    strm2a = 'What is the map width (pixels)?';
    strm3a = 'What is the min Frequency?';
    strm4a = 'What is the max Frequency?';
    strm5a = 'What is the min x parameter?';
    strm6a = 'What is the max x parameter?';
    strmat = {strm1a,strm2a,strm3a,strm4a,strm5a,strm6a};
    xminstrg = round(min(min(min(xparm))));
    xmaxstrg = round(max(max(max(xparm))));
    default = {'300','500','0','200','0','1000'};
    inputmapa = inputdlg(strmat,'New Map Parameters',[1 50],default);
    h = str2double(inputmapa{1});
    w = str2double(inputmapa{2});
    mapFmin = str2double(inputmapa{3});
    mapFmax = str2double(inputmapa{4});
    mapxmin = str2double(inputmapa{5});
    mapxmax = str2double(inputmapa{6});

    i = 1;
    for i = 1: numfiles
    figure(fignum)
    fignum = fignum + 1;
    hold on
    axis([mapxmin mapxmax mapFmin mapFmax])
    himage = imagesc(xparm(:,:,i),Farray,Amp(:,:,i));
    colormap;
    hAxes = himage.Parent;
    ampmax(i) = max(max(Amp(:,:,i)));
    hAxes.CLim = [s,ampmax(i)/10]; 
    xlabel(strcat(namexparm,'(', unitsxparm, ')'));
    ylabel("Frequency(Hz)");
    title(strcat("Waterfall map for: Test ", testname , "-", fn(i)))
    colorbar;
    truesize([h w]);
    hold off
    end

else

disp("no more plots");

end

.....

Answer 1

[Amy Haskins]

The problem is with using == on character vectors. Each character is treated as a separate element and compared individually. This will error when the lengths of the strings you are trying to compare doesn't match.

>> 'no' == 'yes'
Matrix dimensions must agree.

>> 'yes' == 'yes'

ans =

    1×3 logical array

     1   1   1

There are 2 easy solutions. One is to use strcmp. The other is to use the string data type (introduced in R2016b) which will behave more like you were expecting.

>> strcmp('no','yes')

ans =

    logical

     0

>> "no" == "yes"  % String scalars

ans =

    logical

     0

[Kateri Kaminski]

Oh this makes sense. Thanks!