hi i want to ask,why matlab cannot process the condition for the while loop ? Thank you!

clc
clear
close all
%Input data
w=input('Enter the load,w: ');
L=input('Enter the beam length: ');
x=input('Enter specific point: ');
%While loop if false

while (w<1||L<1||x<0||isempty(w)||isempty(L)||isempty(x))
    fprintf("\nPlease recheck input data\n")
    w=input('Enter the load,w: ');
    L=input('Enter the beam length: ');
    x=input('Enter specific point: '); 
    
end

%true input data          
Ra=w*L;
Ma=-w*L.^2/2;
Mx=-w*(L-x).^2/2;
Sx=w*(L-x);

fprintf("\nThe reaction at A is %.2f\n",Ra)
fprintf("The moment at A is %.2f\n",Ma)
fprintf("The bending moment at point %.f is %.2f\n",x,Mx)
fprintf("The shear force at point %.f is %.2f\n",x,Sx)

[Image Analyst]

Works fine for me. What are your initial inputs before the loop and then what are you entering in the loop?

[NUR AIN ATIKAH ABDUL LATIF]

i want to make the process re-input the data if user key-in wrong input like negative value and no input from user

Answer 1

[Steven Lord]

Since you're using the short-circuiting or operator you should check the size of the inputs first. Rather than asking if they're empty, ask if they're not a scalar.

%{
while ~isscalar(w) || ~isscalar(L) || ~isscalar(x) || w < 1 || L < 1 || x < 0
%}

That way if (for example) w was not a scalar the ~isscalar(w) check would make the while condition return false before it gets to the w < 1 part (and throws an error.)

w = 0:5;
~isscalar(w) || w < 1 % false, MATLAB doesn't get to the w < 1 check

ans = logical
   1

w < 1 || ~isscalar(w) % error, w < 1 is logical but not scalar

Operands to the logical and (&&) and or (||) operators must be convertible to logical scalar values.

[NUR AIN ATIKAH ABDUL LATIF]

Thank you!!