How to re-prompt user input if given incorrect value?

I am trying to create a program where the user inputs two numbers that are used as variables. I want to display an error message and re-prompt user input if they give me a non-numerical inout. Here is the code I have so far:

FLAG = false;
while FLAG == false
    input = {'Width of sprinkler field (ft):','Spacing from edge of field (ft):'};
    input = inputdlg(input);
    input = str2double(input);
    yMax = input(1);
    spacing = input(2);  
    if (isnumeric(yMax)==1 && isnumeric(spacing)==1)
        FLAG = true;
    else
        msgbox('ERROR. Input numerical value');
    end
end

Any help would be appreciated, thanks!

Answer 1

[James Tursa]

str2double will turn your inputs into numeric, so you will pass your isnumeric( ) test even if there are problems. Instead, check for NaN. E.g.

if (isnan(yMax)==0 && isnan(spacing)==0)

Side Notes:

input is the name of a MATLAB built-in function. It would be better if you picked a different name for your variable.

You don't really need that FLAG variable for your logic. A simpler approach:

while true
    :
    if (isnan(yMax)==0 && isnan(spacing)==0)
        break;
    end
    msgbox('ERROR. Input numerical value');
end

[Niall McKinnon]

Thank you!