Contours

The pygmt.Figure.contour method can plot contour lines from a table of points by direct triangulation. The data to the triangulation can by provided in one of three options:

1: x, y, z 1d numpy.ndarray data columns

2: data 2d 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 are deciding on the contours intervals and intervals of the annotation on the contours respectively.

In this example we supply the data as 1d numpy.ndarray with the x, y, and z parameters and draw the contours using a 0.5p pen with contours every 5 z values and annotations every 20 z values.

Out:

<IPython.core.display.Image object>

import numpy as np
import pygmt

# building the contours underling 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",
    # passing the data as 3 1d data columns
    x=x,
    y=y,
    z=z,
    # set the contours z values intervals to 5
    levels=5,
    # set the contours annotation intervals to 20
    annotation=20,
)
fig.show()