4-d graph.

### 7.4.4 4-d graph.

plotfunc represents a complex expression E (such that re(E) is not identically 0 on the discretization mesh) by the surface z=abs(E) where arg(E) defines the color from the rainbow. This gives an easy way to see the points having the same argument. Note that if re(E)==0 on the discretization mesh, it is the surface z=E/i that is represented with rainbow colors (cf 7.4.3).
The first argument of plotfunc is E, the remaining arguments are the same as for a real 3-d graph (cf 7.4.2).
Input :

plotfunc((x+i*y)`^`2,[x,y])

Output :

A graph 3D of z=abs((x+i*y)`^`2 with the same color for points having the same argument

Input :

plotfunc((x+i*y)`^`2x,[x,y], display=filled)

Output :

The same surface but filled

We may specify the range of variation of x and y and the number of discretization points.
Input :

plotfunc((x+i*y)`^`2,[x=-1..1,y=-2..2], nstep=900,display=filled)

Output :

The specified part of the surface with x between -1 and 1, y between -2 and 2 and with 900 points