According to Single-page reference in R

The data the describes the coordinates of the surface is set in

`z`

. Data in`z`

should be a 2D list. Coordinates in`x`

and`y`

can either be 1D lists or {2D arrays} (e.g. to graph parametric surfaces). If not provided in`x`

and`y`

, the x and y coordinates are assumed to be linear starting at 0 with a unit step. The color scale corresponds to the`z`

values by default. For custom color scales, use`surfacecolor`

which should be a 2D list, where its bounds can be controlled using`cmin`

and`cmax`

.

What is `z`

exactly? I expected it to be `z`

values, so I would expect it to be 1D, but apparently it’s expecting a 2D array? What do I plug in there?