MATLAB Function Reference  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 `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.

C = [value1xdata(1)xdata(2)...value2xdata(1)xdata(2)...;
`    `dim1`  `ydata(1)ydata(2)...dim2ydata(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

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