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 contour_generator()
function and call it to create and return the
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 lines()
is controlled by
the line_type
argument passed to 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 Fill type.
Note
The format of data returned by filled()
is controlled by
the filled_type
argument passed to 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 contourpy.util
module:
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 contourpy.util.bokeh_renderer
module. In the example above change the line
from contourpy.util.mpl_renderer import MplRenderer as Renderer
into
from contourpy.util.bokeh_renderer import BokehRenderer as Renderer
Output for the BokehRenderer
renderer is sent to your web browser.