How can I repeat question until valid input is entered?

Question

youruined_everything 2016-11-25

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https://ww2.mathworks.cn/matlabcentral/answers/313993-how-can-i-repeat-question-until-valid-input-is-entered

评论： bio lim 2016-11-27

I have a bit of code that asks two questions. I want the questions to continue to be prompted until a valid response is given. For the first question, they need to enter in any number greater than zero. For the second question they must enter in A, B, C, D, or E. Any other response should either repeat the question or potentially rephrase the question to emphasize the correct format. Here is the code that works as long as they enter the response correctly.

%Input
fpc = input('Enter specified compressive strength (psi): ');
Facility = input('Chooose facility letter in upper-case (A-E): ', 's');

And just to show one of the things I've tried:

while Facility ~= 'A,B,C,D,E';
Facility = input('Chooose facility letter in upper-case (A-E): ', 's');
end

And this actually does work, unless the user enters in a value that is more than one character long, then I get a 'matrix dimensions must agree', which doesn't make sense to me. In any case, I'm sure there is a better way to do this.

Thank you

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Answer 1

bio lim 2016-11-25

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编辑：bio lim 2016-11-26

在 MATLAB Online 中打开

What if you implement it using a while loop?

%Input
clc;
clear all;
close all;
fpc = input('Enter specified compressive strength (psi): ');
coffee = 0;
while ~coffee
Facility = input('Chooose facility letter in upper-case (A-E): ', 's');
if ~ismember(Facility, {'A','B','C','D','E'})
        coffee = 0;
else coffee = 1;
end
end

This will guarantee that the Facility will take a character from A-E, and if not, will continue to loop.

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youruined_everything 2016-11-25

编辑：youruined_everything 2016-11-25

在 MATLAB Online 中打开

I tried to use a while loop as indicated in my post, but I will try yours. In principle I understand how while loops work, but I have very little experience with them (or matlab and programming for that matter). Could you explain what your code is going to do? Specifically the tilde portion.

while ~coffee

I understand that while loops executes a statement until it is false, but I suppose I don't understand the syntax.

And just in case it's important here is the next snippet of code.

% Develop all data files for all facilities
if Facility == 'A'
    myfacdata = textread ('FacA.txt');
elseif Facility == 'B'
    myfacdata = textread ('FacB.txt');
elseif Facility == 'C'
    myfacdata = textread ('FacC.txt');
elseif Facility == 'D'
    myfacdata = textread ('FacD.txt');
elseif Facility == 'E'
    myfacdata = textread ('FacE.txt');    
end
      ntests = length(myfacdata);