This question made me wonder whether questions about creating simple 2D plots are considered on topic or not. They don't seem to require very specialised computer graphics knowledge, so they'd probably get a decent answer on SO as well. Yet, they're undoubtedly about generating graphical output computationally.
If these are deemed "too simple" or otherwise off topic, where do we draw the line? Surely an elaborate 3D surface plot or a question about plotting B-splines would be on topic.
Possibly, it may depend. After some thinking this must be offtopic. Asking for how to implement a graph library drawing internals is almost certainly on topic.
Another thing is: Is it constructive to ask this here? There are forums that most certainly would answer faster in this case.
Anyway what we do need is some sort of litmus test for whether or not something is graphics related. Quite obviously it's not enough that you want to draw a picture, not even a nice one. Because otherwise every graphics design question could be applicable here.
Also lets look at our on topics page it states
Questions about a specific graphics API
Are on topic. So that means this is possibly on topic. But the question is about scientific plotting and as such its not really drawing anything new just using precanned graphing functions. Otherwise most Mathematica questiosn would be on topic too.
I would say that the question does not really relate to graphics drawing but rather sending wrong data to the drawing algorithm. And while it may be debugging its still not enough about graphics.
Finally the deciding factor is, specific graphing tools, should be offtopic same way as using a specific modeling application is offtopic. In this case its like asking how to do this and that in maya, only this and that here is R and modelling is the thing he does and graphing is just the reflection of the modeling.
