Not effective validation algorithm for input format

Hello everyone, I am asking as input, coordinates of quadrilateral vertices and I am adding an extra layer for format checking. Simply speaking inputs must be numerical.

vx=zeros(1,4);
vy=zeros(1,4);
vertices=['A'; 'B'; 'C'; 'D'];
fprintf('\nPlease enter the coordinates of vertices:\n');
for cnt=1:4
    fprintf('\n For vertix <strong> %s </strong>', vertices(cnt));
    fprintf(' :\n');
    vx(cnt) = input('  Χ=');
    vxtest=isnumeric(vx(cnt));
    while vxtest==0
        fprintf('ERROR: Non numerical character, try again.\n');
        vx(cnt) = input('  Χ=');
        vxtest=isnumeric(vx(cnt));
    end
    vy(cnt) = input('  Y=');
    vytest=isnumeric(vy(cnt));
    while vytest==0
        fprintf('ERROR: Non numerical character, try again.\n');
        vy(cnt) = input('  Y=');
        vytest=isnumeric(vy(cnt));
    end
end
vx=vx(1:4);
vy=vy(1:4);

But still it is possible to put a string as an input and continue to the next coordinate. At the end, there is an output area of a quadrilateral with vertices out of string coordinates.

Thanks in advance!

Answer 1

[Ameer Hamza]

Try this

vx=zeros(1,4);
vy=zeros(1,4);
vertices=['A'; 'B'; 'C'; 'D'];
fprintf('\nPlease enter the coordinates of vertices:\n');
for cnt=1:4
    fprintf('\n For vertix <strong> %s </strong>', vertices(cnt));
    fprintf(' :\n');
    temp = input('  Χ=');
    vxtest=isnumeric(temp);
    vx(cnt) = temp;
    while vxtest==0
        fprintf('ERROR: Non numerical character, try again.\n');
        temp = input('  Χ=');
        vxtest=isnumeric(temp);
        vx(cnt) = temp;
    end
    temp = input('  Y=');
    vytest=isnumeric(temp);
    vy(cnt) = temp;
    while vytest==0
        fprintf('ERROR: Non numerical character, try again.\n');
        temp = input('  Y=');
        vytest=isnumeric(temp);
        vy(cnt) = temp;
    end
end
vx=vx(1:4);
vy=vy(1:4);

[Destro Katramis]

I don't know what it was causing it but that fixed it! Thank you very much Ameer!!

[Ameer Hamza]

I am glad to be of help!

The problem was caused because vx is a numeric matrix (because of line vx=zeros(1,4)). So when you run the line

vx(cnt) = input('  Χ=');

the character is converted to a numeric value using ASCII table, and isnumeric() function return true.