RandomGraph[{n, m}] gives a pseudorandom graph with n vertices and m edges.RandomGraph[{n, m}, k] gives a list of k pseudorandom graphs.RandomGraph[gdist, ...] samples from ...

RandomVariate[dist] gives a pseudorandom variate from the symbolic distribution dist.RandomVariate[dist, n] gives a list of n pseudorandom variates from the symbolic ...

RangeFilter[image, r] filters image by replacing every pixel by the difference of the maximum and minimum in its range r neighborhood. RangeFilter[data, r] applies a range ...

RankedMin[list, n] gives the n\[Null]^th smallest element in list.

As of Version 6.0, RasterArray has been superseded by new capabilities in Raster.

Rasterize[g] returns a rasterized graphic of g. Rasterize[g, elem] gives the element elem associated with the rasterized form of g.

Raster[{{a_11, a_12, ...}, ...}] is a two-dimensional graphics primitive which represents a rectangular array of gray cells. Raster[{{{r_11, g_11, b_11}, ...}, ...}] ...

RasterSize is an option for Rasterize and related functions that determines the absolute pixel size of the raster generated.

Rationalize[x] converts an approximate number x to a nearby rational with small denominator. Rationalize[x, dx] yields the rational number with smallest denominator that lies ...

Rational is the head used for rational numbers.