error checking wont replace old input

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David Phung 2014-11-16

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评论： David Phung 2014-11-16

This is my code and I want to error check it for the person to input a vector of grades that are from 0 to ten. Every time I run it once with the correct grades [1 2 3], it works. However, if I run it with a wrong vector [-1 2 3] then a correct one [1 2 3], it keeps telling me to enter another vector. I checked my workspace and it appears that the first vecgrade isnt being replaced by the second one.

   clear all; clc
    vecgrade=input('Enter a vector of quiz grades: \n');
    vecchecker=vecgrade>=0 & vecgrade<=10;
    while all(vecchecker)==0
        vecgrade=input('Please enter another vector of quiz grades: \n');
        vecchecker=vecgrade<0 & vecgrade>10;
    end
    vecgrade

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Answer 1

Geoff Hayes 2014-11-16

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David - your re-initialization of vecchecker in the while loop uses a different condition than the one outside of the while loop. Note that if

 vecgrade = [1 2 3];
 vecchecker=vecgrade<0 & vecgrade>10;

then

 vecchecker =
     0     0     0

Which makes sense because the condition is saying if the grade is less than zero and greater than ten - which is impossible, so the vector is all zeros (false).

Change your re-initialization of this local variable to be the same as that outside of the loop

vecchecker=vecgrade>=0 & vecgrade<=10;

and your code should work fine.