MATLAB Function Reference |

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 `i`

, use `contourc(Z,[i i])`

.

```
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*-axis limits. `x`

and `y`

must be monotonically increasing.

**Remarks**

`C`

is a two-row matrix specifying all the contour lines. Each contour line defined in matrix `C`

begins with a column that contains the value of the contour (specified by `v`

and used by `clabel`

), and the number of `(x,y)`

vertices in the contour line. The remaining columns contain the data for the `(x,y)`

pairs.

value1

xdata(1)

xdata(2)...

value2

xdata(1)

xdata(2)...;` `

dim1` `

ydata(1)

ydata(2)...

dim2

ydata(1)

ydata(2)...]
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`

.

**See Also **

`clabel`

, `contour`

, `contour3`

, `contourf`

Contour Plots for related functions

The Contouring Algorithm for more information

contour3 | contourf |