MATLAB: How can i do let Matlab returns variable name when i check its value

variablevariable name

Assumed that, i have a code as below:
x=input('x = ');
y=input('y= ');
z=input(z= ');
...and so on.
And my condition is value of any x , y or z… (that user will give into accrossding to keyboard) is must be positive. And i mean is after user give into value of variables above. How can i do to know what variable is negative. For example, I want to my program warning that: " Variable x is negative", My code that i tried. I create a vecto that called "Ktra" and use a for loop.
x=input('x= ');
y=input('y= ');
z=input('z= ');
Ktra=[x y z];
iam = 1;
for i=1:length(Ktra)
    if Ktra(i)<0
        disp('Gia tri nhap can lon hon 0');
        tprintf('So thu tu cua so bi am la: %d \n', iam);
    end
end
Thank you so much!

Best Answer

This works for any number of variables, just add them to the cell array V:
V = {'x','y','z'};
S = struct();
for k = 1:numel(V)
    str = sprintf('Please enter %s value: ',V{k});
    tmp = str2double(input(str,'s'));
    if tmp<0
        disp('Gia tri nhap can lon hon 0');
        fprintf('So thu tu cua so bi am la: %s \n',V{k})
    end
    S.(V{k}) = tmp;
end
When run it gives this:
>>
Please enter x value: 23
Please enter y value: 5
Please enter z value: -9
Gia tri nhap can lon hon 0
So thu tu cua so bi am la: z 
>>
and of course the values can be simply accessed using the structure fields:
>> S.x
ans =
    23
>> S.z
ans =
    -9
Note also that I used the faster and more secure option of getting input to return a string: str2double(input(...,'s')), as opposed to the buggy and unpredictable input(...).
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