Help determining values of a vector

Question

Julian Epps 2016-6-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/292298-help-determining-values-of-a-vector

评论： Julian Epps 2016-6-26

Hello, I am writing a code that asks the user to input a number a values then takes those values and puts them into an array. Then evaluates each element of the array to determine if it is pos, neg, even, or odd. Here's what I have

function [Poseven]= Vect(UserNum);
    str = inputdlg('Enter 10 numbers seperated by spaces or commas');
      UserNum = str2num(str{1});
      if mod(UserNum, 2) == 0, UserNum > 0; 
         Poseven = UserNum(1,1:end)
      end
 end

The only thing I am not understanding is why or how rather to display the numbers of the original vector where the modulus value is zero and greater than zero.

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Answer 1

Walter Roberson 2016-6-25

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https://ww2.mathworks.cn/matlabcentral/answers/292298-help-determining-values-of-a-vector#answer_226746

在 MATLAB Online 中打开

Your lines

      if mod(UserNum, 2) == 0, UserNum > 0; 
         Poseven = UserNum(1,1:end)
      end

are the same as

      if mod(UserNum, 2) == 0
         UserNum > 0; 
         Poseven = UserNum(1,1:end)
      end

which calculates whether UserNum > 0 and then throws away the result of the comparison. If you want to combine conditions, you need to use one of &&, ||, &, or |

Note: you probably want to use either a loop or logical indexing.

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Julian Epps 2016-6-26

在 MATLAB Online 中打开

Oh okay so this will check the two conditions instead of overwriting one with the other, Thanks! The other problem I am facing is that I need to return only the positive even numbers of of the original UserNum. the lines :

 if mod(UserNum, 2) == 0 & (UserNum > 0);
        Poseven = UserNum(1,1:end)
 Don't seem to be returning those original values but I am not getting an error when I run it, any help or explanation as to why?

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