How do I change the display of my answers if condition is not met?

Here is what I have so far:

*format compact                          
a=input('Enter value for side a: ');    
if a <= 0                               
  disp('Not a valid input.');break;   
end
b=input('Enter value for side b: ');    
if b <= 0                               
  disp('Not a valid input.');break;   
end
c=input('Enter value for side c: ');    
if c <= 0                               
  disp('Not a valid input.');break;   
if a > b+c                              
  fprintf('\n');                      
  disp('Error: Side "a" must be less than the sum of sides b & c.') % 
elseif b > a+c                          
  fprintf('\n');                      
  disp('Error: Side "b" must be less than the sum of sides a & c.')
elseif c > a+b                          
  fprintf('\n');                      
  disp('Error: Side "c" must be less than the sum of sides a & b.')
end
fprintf('\n');                          
A=acosd((b^2+c^2-a^2)/(2*b*c)); 
B=acosd((a^2+c^2-b^2)/(2*a*c)); 
C=acosd((a^2+b^2-c^2)/(2*a*b)); 
disp('Results:')
fprintf('Angle A = %G',A);disp(' degrees') 
fprintf('Angle B = %G',B);disp(' degrees') 
fprintf('Angle C = %G',C);disp(' degrees') *

When the conditions that provide the "Error" message are not met, I still get something like:

Angle A = 180 degrees Angle B = 0 degrees Angle C = 0 degrees

But I would like to have my program display something when there could be no viable answers, like:

Angle A = NaN degrees Angle B = NaN degrees Angle C = NaN degrees

or

Any message I choose.

Answer 1

[Sean de Wolski]

Why don't you use error() instead of disp('...') to actually abort the program when the error is encountered.

Or, to keep what you have and make the if-decision tree work:

if

elseif

elseif

else
   %we haven't errored, woohoo!
    fprintf('\n');                          
    A=acosd((b^2+c^2-a^2)/(2*b*c)); 
    B=acosd((a^2+c^2-b^2)/(2*a*c)); 
    C=acosd((a^2+b^2-c^2)/(2*a*b)); 
    disp('Results:')
    fprintf('Angle A = %G',A);disp(' degrees') 
    fprintf('Angle B = %G',B);disp(' degrees') 
    fprintf('Angle C = %G',C);disp(' degrees') *
end