Quick start

Contour generator

Firstly create a simple 2x2 grid of z values using Python lists:

z = [[0.0, 0.1], [0.2, 0.3]]

Import the :func:~contourpy.contour_generator function and call it to create and return the :class:~contourpy.ContourGenerator object that will be used to contour the z values:

from contourpy import contour_generator cont_gen = contour_generator(z=z) cont_gen <contourpy._contourpy.SerialContourGenerator object at 0x7ff827fc4a30>

The hexadecimal number will be different, it is the address of the pybind11_-wrapped C++ object.

Contour lines

Create some contour lines at a z-level of 0.25:

lines = cont_gen.lines(0.25) lines [array([[0.5, 1.0], [1. , 0.75]])]

The output is a list of lines, here just one line that is a NumPy_ array of shape (2, 2) consisting of two (x, y) points from (0.5, 1) to (1, 0.75).

.. note::

The format of data returned by :meth:~contourpy.ContourGenerator.lines is controlled by the line_type argument passed to :func:~contourpy.contour_generator.

Filled contours

Create some filled contours between the z-levels of 0.15 and 0.25:

filled = cont_gen.filled(0.15, 0.25) filled ([array([[0. , 1. ], [0. , 0.75], [1. , 0.25], [1. , 0.75], [0.5, 1. ], [0. , 1. ]])], [array([0, 6], dtype=uint32)])

The output data is more complicated, it is a tuple of two lists each of which has a length of one corresponding to a single polygon. The first NumPy_ array has shape (6, 2) and is the (x, y) coordinates of the 6 points that make up the polygon; the first and last points are the same. The second NumPy_ array is an integer array of offsets into the points array; here the offsets cover the whole length of the points array indicating that it is a single polygon. This is explained further in :ref:fill_type.

.. note::

The format of data returned by :meth:~contourpy.ContourGenerator.filled is controlled by the filled_type argument passed to :func:~contourpy.contour_generator.

Graphical output

It is easier to understand the contour lines and filled contours by looking at graphical output. Here is the full example using the Matplotlib_ renderer from the :mod:contourpy.util module:

.. plot:: :separate-modes: :source-position: below

from contourpy import contour_generator from contourpy.util.mpl_renderer import MplRenderer as Renderer

z = [[0.0, 0.1], [0.2, 0.3]] cont_gen = contour_generator(z=z) lines = cont_gen.lines(0.25) filled = cont_gen.filled(0.15, 0.25)

renderer = Renderer(figsize=(4, 2.5)) renderer.filled(filled, cont_gen.fill_type, color="gold") renderer.lines(lines, cont_gen.line_type, color="red", linewidth=2) renderer.show()

Alternatively you can use the Bokeh_ renderer from the :mod:contourpy.util.bokeh_renderer module. In the example above change the line

.. code-block:: python

from contourpy.util.mpl_renderer import MplRenderer as Renderer

into

.. code-block:: python

from contourpy.util.bokeh_renderer import BokehRenderer as Renderer

Output for the Bokeh_ renderer is sent to your web browser.