Colorbar

The pygmt.Figure.colorbar method creates a color scalebar. We must specify the colormap via the cmap argument, and set the placement via the position argument. The full list of color paletted tables can be found at https://www.generic-mapping-tools.org/gmt/latest/cookbook/cpts.html. You can set the position of the colorbar using the following options:

• j/J: justified inside/outside the mapframe using any 2 character combination of vertical (T op, M iddle, B ottom) and horizontal (L eft, C enter, R ight) alignment codes, e.g. position=”jTR” for top right.
• g: using map coordinates, e.g. position=”g170/-45” for longitude 170E, latitude 45S.
• x: using paper coordinates, e.g. position=”x5c/7c” for 5cm,7cm from anchor point.
• n: using normalized (0-1) coordinates, e.g. position=”n0.4/0.8”.

Note that the anchor point defaults to the bottom left (BL). Append +h to position to get a horizontal colorbar instead of a vertical one. For more advanced styling options, see the full option list at https://www.generic-mapping-tools.org/gmt/latest/colorbar.html.

import pygmt

fig = pygmt.Figure()
fig.basemap(region=[0, 3, 6, 9], projection="t0/3c", frame=True)

# Create a colorbar suitable for surface topography- oleron

fig.colorbar(
    cmap="oleron",
    position="jTC+w6c/1c+h",  # justified inside map frame (j) at Top Center (TC)
    box=True,
    frame=["+Loleron", "xaf", "y+lm"],
    scale=10,
)
# Create a colorbar designed for seismic tomography- roma
fig.colorbar(
    cmap="roma",
    position="x1.2c/4.75c+w6c/1c+h",  # plot using paper coordinates (x) at 1.2cm,4.75cm
    box=True,
    frame=["+Lroma", "xaf", "y+lm/s"],
    scale=10,
)
# Create a colorbar showing the scientific rainbow - batlow
fig.colorbar(
    cmap="batlow",
    position="g0.45/6.6+w6c/1c+h",  # plot using map coordinates (g) at lon/lat 0.45/6.6
    box=True,
    frame=["+Lbatlow", "xaf", r"y+l\260C"],
    scale=10,
)

fig.show()