Documentation

# contourc

Low-level contour plot computation

## Syntax

```C = contourc(Z) C = contourc(Z,n) C = contourc(Z,v) C = contourc(x,y,Z) C = contourc(x,y,Z,n) C = contourc(x,y,Z,v) ```

## Description

`contourc` calculates the contour matrix `C` used by `contour`, `contour3`, and `contourf`. The values in `Z` determine the heights of the contour lines with respect to a plane. The contour calculations use a regularly spaced grid determined by the dimensions of `Z`.

`C = contourc(Z)` computes the contour matrix from data in matrix `Z`, where `Z` must be at least a 2-by-2 matrix. The contours are isolines in the units of `Z`. The number of contour lines and the corresponding values of the contour lines are chosen automatically.

`C = contourc(Z,n)` computes contours of matrix `Z` with `n` contour levels.

`C = contourc(Z,v)` computes contours of matrix `Z` with contour lines at the values specified in vector `v`. The length of `v` determines the number of contour levels. To compute a single contour of level `k`, use `contourc(Z,[k k])`.

`C = contourc(x,y,Z)`, ```C = contourc(x,y,Z,n)```, and `C = contourc(x,y,Z,v)` compute contours of `Z` using vectors `x` and `y` to determine the x and y values. `x` and `y` must be monotonically increasing.

## Tips

For more information on the contour matrix, see the `ContourMatrix` property for contour objects.

Specifying irregularly spaced `x` and `y` vectors is not the same as contouring irregularly spaced data. If `x` or `y` is irregularly spaced, `contourc` calculates contours using a regularly spaced contour grid, then transforms the data to `x` or `y`.