How to make a loop repeat itself when user typed the wrong letter?

Hi all,

I created a loop where the user need to state whether the already stated filepath in the script is correct. If not they can select the desired filepath. I'm also trying to make the user type 'y' or 'n' and if they have typed anything else i want the loop to repeat itself unitil the correct letter is typed. But i am struggling to do the last part.

This is what the coding looks like right now:

p='E:\...'; 
fprintf('Data to be analysed is located in: \n');
fprintf('<strong>%s\n</strong>', p) 
x=input('\nIs the file path correct? Y/N: ','s'); 
if strcmpi(x, 'Y');
        disp('Thank you, the file path has been saved.')
        ...
    elseif strcmpi(x, 'N');
        disp('Please select the required file path.')
        p=uigetdir(path);
        fprintf('Thank you, the new file path has been saved as: \n');
        fprintf('<strong>%s\n</strong>', p);
        ...
    else strcmpi(x,'');
        disp('Please type "Y" or "N"');
        x=input('Is the file path correct? Y/N: ','s');
        ...
end

As you can see the last part, if the user type the wrong letter twice it will stop the loop but i want it to repeat until the correct letter is typed.

Any suggestion on how i can do so?

Thank you :)

Answer 1

[Antoni Garcia-Herreros]

Hello S C,

You should use while instead of for loop.

p='E:\...'; 
fprintf('Data to be analysed is located in: \n');
fprintf('<strong>%s\n</strong>', p) 
x=input('\nIs the file path correct? Y/N: ','s'); 
while ~strcmpi(x, 'Y') && ~strcmpi(x, 'N') ; % It will only exit this loop when Y or N are pressed

    disp('Please type "Y" or "N"');
    x=input('Is the file path correct? Y/N: ','s');
end
if strcmpi(x, 'Y');
        disp('Thank you, the file path has been saved.')
elseif strcmpi(x, 'N');
disp('Please select the required file path.')
p=uigetdir(path);
fprintf('Thank you, the new file path has been saved as: \n');
fprintf('<strong>%s\n</strong>', p);
end

Hope this helps!

[S C]

Hi Antoni, thank you. This worked as i want.

Answer 2

[Abb]

You can achieve this by putting the code block inside a while loop and using a flag variable to control the loop. Here's an example:

p='E:\...'; 
fprintf('Data to be analysed is located in: \n');
fprintf('<strong>%s\n</strong>', p) 

flag = false;
while ~flag
    x=input('\nIs the file path correct? Y/N: ','s'); 
    if strcmpi(x, 'Y');
        disp('Thank you, the file path has been saved.')
        flag = true;
    elseif strcmpi(x, 'N');
        disp('Please select the required file path.')
        p=uigetdir(path);
        fprintf('Thank you, the new file path has been saved as: \n');
        fprintf('<strong>%s\n</strong>', p);
    else 
        disp('Please type "Y" or "N"');
    end
end

This will continue to prompt the user for input until they enter either "Y" or "N". The flag variable is initially set to false, and the loop will continue to run until it is set to true when the user enters "Y".

[S C]

Hi, thank you. This worked as i wanted as well but i needed to add 'flag=true' at the end of the elseif statement (between line 15 and 16).