Contours

The pygmt.Figure.contour method can plot contour lines from a table of points by direct triangulation. The data for the triangulation can be provided using one of three methods:

1. x, y, z 1-D numpy.ndarray data columns.

2. data 2-D numpy.ndarray data matrix with 3 columns corresponding to x, y, z.

3. data path string to a file containing the x, y, z in a tabular format.

The parameters levels and annotation set the intervals of the contours and the annotation on the contours respectively.

In this example we supply the data as 1-D numpy.ndarray with the x, y, and z parameters and draw the contours using a 0.5p pen with contours every 10 z values and annotations every 20 z values.

import numpy as np
import pygmt

# build the contours underlying data with the function z = x^2 + y^2
X, Y = np.meshgrid(np.linspace(-10, 10, 50), np.linspace(-10, 10, 50))
Z = X**2 + Y**2
x, y, z = X.flatten(), Y.flatten(), Z.flatten()


fig = pygmt.Figure()
fig.contour(
    region=[-10, 10, -10, 10],
    projection="X10c/10c",
    frame="ag",
    pen="0.5p",
    # pass the data as 3 1-D data columns
    x=x,
    y=y,
    z=z,
    # set the contours z values intervals to 10
    levels=10,
    # set the contours annotation intervals to 20
    annotation=20,
)
fig.show()