Note
Click here to download the full example code
Making your first figure¶
Welcome to PyGMT! Here we’ll cover some of basic concepts, like creating simple figures and naming conventions.
Note
This tutorial assumes the use of a Python notebook, such as IPython
or JupyterLab.
To see the figures while using a Python script instead, use
fig.show(method="external")
to display the figure in the default PDF viewer.
To save the figure, use fig.savefig("figname.pdf")
where "figname.pdf"
is the desired name and file extension for the saved figure.
Loading the library¶
All modules and figure generation is accessible from the pygmt
top level
package:
Creating figures¶
All figure generation in PyGMT is handled by the pygmt.Figure
class.
Start a new figure by creating an instance of this class:
fig = pygmt.Figure()
Add elements to the figure using its methods. For example, let’s use
pygmt.Figure.basemap
to start the creation of a map. We’ll use the region
parameter
to provide the longitude and latitude bounds, the projection
parameter to set
the projection to Mercator (M) and the map width to 15 cm, and the frame
parameter to generate a frame with automatic tick and annotation spacings.
fig.basemap(region=[-90, -70, 0, 20], projection="M15c", frame=True)
Now we can add coastlines using pygmt.Figure.coast
to this map using the
default resolution, line width, and color:
fig.coast(shorelines=True)
To see the figure, call pygmt.Figure.show
:
fig.show()
Out:
You can also set the map region, projection, and frame type directly in other methods
without calling gmt.Figure.basemap
:
fig = pygmt.Figure()
fig.coast(shorelines=True, region=[-90, -70, 0, 20], projection="M15c", frame=True)
fig.show()
Out:
Saving figures¶
Use the method pygmt.Figure.savefig
to save your figure to a file. The figure
format is inferred from the extension.
fig.savefig("central-america-shorelines.png")
Note for experienced GMT users¶
You have probably noticed several things that are different from classic command-line GMT. Many of these changes reflect the new GMT modern execution mode that is part of GMT 6.
As a general rule, the
ps
prefix has been removed from allps*
modules (PyGMT methods). For example, the name of the GMT 5 modulepscoast
iscoast
in GMT 6 and PyGMT. The exceptions are:psxy
which is nowplot
,psxyz
which is nowplot3d
, andpsscale
which is nowcolorbar
.More details can be found in the GMT cookbook introduction to modern mode.
A few are PyGMT exclusive (like the savefig
method).
The PyGMT parameters (called options or arguments in GMT) don’t use the GMT 1-letter syntax (R, J, B, etc). We use longer aliases for these parameters and have some Python exclusive names. The mapping between the GMT parameters and their PyGMT aliases should be straightforward. For some modules, these aliases are still being developed.
Parameters like
region
can takelists
as well as strings like1/2/3/4
.If a GMT option has no arguments (like
-B
instead of-Baf
), use aTrue
in Python. An empty string would also be acceptable. For repeated parameters, such as-B+Loleron -Bxaf -By+lm
, provide alist
:frame=["+Loleron", "xaf", "y+lm"]
.There is no output redirecting to a PostScript file. The figure is generated in the background and will only be shown or saved when you ask for it.
Total running time of the script: ( 0 minutes 2.858 seconds)