> Do you mean, if you have a given y value, and you are describing "is the point (x,y) inside the circle" as a function of x, then if you pick the y value to be

> Do you mean, if you have a given y value, and you are describing "is the point (x,y) inside the circle" as a function of x, then if you pick the y value to be further than r away from the the y coordinate of the center of the circle, where r is the radius, that the function stops depending on x and for all x, is "no" ? Yes > I'm really not sure what point you are trying to make. The point is that it is non-linear, and people want linear “explanations”. If you imagine that x is say income, then people want simple explanations for the effect of income on the model. People don’t like it if you say that, well sometimes income has an effect and sometimes it doesn’t. They don’t like it when you say that it actually depends on the relationship of a number of other variables in a non-linear way. They tend to assume that you’re hand-waving or making excuses, when instead what they’re asking for is a mathematical impossibility.