plot/contour

(isoline [f x-min :float x-max :float y-min :float y-max :float samples :int level :float style :int label :cstr] :int)

draw a single f(x,y)=level contour.

(contours [f x-min :float x-max :float y-min :float y-max :float samples :int n :int styles :int label :cstr] :int)

draw multiple automatically spaced contour levels.

(contour-intervals [f x-min :float x-max :float y-min :float y-max :float samples :int n :int fills :int label :cstr] :int)

fill contour bands using sampled cells.

(color-field [f x-min :float x-max :float y-min :float y-max :float samples :int alpha :float] :int)

color sampled cells by f(x,y)->color-idx.