MATLAB: While Loop regarding user input type stuck on infinite else loop

infinite loopwhile loop

I need to check user input to make sure it's a number. The first part of the while loop works if i input a number, but the 'else' part gets stuck on infinite loop if I input something else, and it won't go out even if I input a number. 
%Part of a Program to calculate equivalent resistance for series and parallel circuits
n = input('Enter Number of resistors: ')
for count = 1:n  
    %input resistance values into an array
    R(count) = input(['Enter the value of Resistor ' num2str(count) ': ']); 
    flag = false; 
     while ~flag 
          num = isnumeric(R(count));    %check if resistance input is a number
          if num == true  %This part works and i can get through the whole for loop if I enter numbers correctly
               flag = true;
    
          else  %This part gets stuck on an infinite loop even if I enter a number
               disp('incorrect entry');
               R(count) = input(['Enter the value of Resistor ' num2str(count) ': ']);   
   
end 
end   
end

Best Answer

The data type of R is not changing, so if you create it as a char, it will never be numeric. If you want to use this setup, you need to use a cell array instead. Another method is to use a temporary variable and store that in R once it is valid:
n = input('Enter Number of resistors: ');
R=zeros(1,n);
for count = 1:n
    tmp=NaN;%enter loop
    while isnan(tmp)
        tmp = input(['Enter the value of Resistor ' num2str(count) ': '],'s');
        tmp=str2double(tmp);
    end
    R(count)=tmp;
end
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