How can I make my function or variable defined if it is undefined?

Trying to run a code but it keeps giving me the error that 'cr' is undefined. I don't know why.

R=input('Enter the R value for the RGB color model:');
G=input('Enter the G value for the RGB color model:');
B=input('Enter the B value for the RGB color model:');
if(0>R||R>255)
  disp('Invalid RGB value.')
  return;
elseif(0>G||G>255)
  disp('Invalid RGB value.')
  return;
elseif(0>B||B>255)
  disp('Invalid RGB value.')
  return;
elseif(R==G==B)
  cr='Gray';
elseif(R>=G>=B)
  cr='Red-Yellow';
elseif(G>R>=B)
  cr='Yellow-Green';
elseif(G>=B>R)
  cr='Green-Cyan';
elseif(B>G>R)
  cr='Cyan-Blue';
elseif(B>R>=G)
  cr='Blue-Magenta';
elseif(R>=B>G)
  cr='Magenta-Red';
else
  disp('Error.')
end
fprintf('%s',cr)

Answer 1

[Matt J]

This

G>=B>R

should really be

 G>=B && B>R

The same with the rest of your triple logical expressions.