R component pixel extraction

i have equation R(x,y)=sqrt(x^2 + y^2)..so i need to compute this equation. x and y are individual pixels from color R. please help me any one ..thank you.

[Ryan]

What exactly are you trying to do? Are you trying to draw a circle? Are you trying to perform a process on an image? On two vectors? Are you trying to extract that "red" channel from an image?

[Image Analyst]

Beats me. Definitely needs clarification. If they're trying to do something with circles, perhaps the Circle FAQ will help.