`contourc`

Computes contour line coordinates without drawing them.

Syntax

C = contourc(Z)

Contour matrix for automatically chosen levels of Z.

C = contourc(Z, levels)

Uses the given number of levels or level values.

C = contourc(x, y, Z, levels)

Uses the coordinate vectors x and y.

Description

contourc is the numerical core behind contour. Use it when you need the line coordinates as data, for example to measure a level curve or to plot it with plot. A closed curve repeats its first point at the end.

Input arguments

Z: Matrix of values, at least 2 by 2.
x, y: Coordinate vectors matching the columns and rows of Z.
levels: Number of levels, or a vector of level values. Repeat a value, as in [v v], to get a single level.

Output arguments

C: Two-row matrix. Each line starts with a column holding the level (row 1) and the number of points (row 2), followed by that many columns of x (row 1) and y (row 2) coordinates.

Example

Coordinates of one level

[X, Y] = meshgrid(-2:2);
Z = X.^2 + Y.^2;
C = contourc(Z, [1 1])

Output

C = 2×6

     1     3     2     3     4     3
     5     2     3     4     3     2

contourc