Gallery example "Legend": Update regarding input data and multi-column legends (#2762)

Co-authored-by: Michael Grund <[email protected]>
Co-authored-by: Dongdong Tian <[email protected]>

Author: 3 people

examples/gallery/embellishments/legend.py

@@ -3,32 +3,60 @@
 ======
 
 The :meth:`pygmt.Figure.legend` method can automatically create a legend for
-symbols plotted using :meth:`pygmt.Figure.plot`. Legend entries are only
-created when the ``label`` parameter is used. For more complicated legends,
-including legends with multiple columns, users have to write an ASCII file
-with instructions for the layout of the legend items and pass it
-to the ``spec`` parameter of :meth:`pygmt.Figure.legend`. For details on
-how to set up such a file, please see the GMT documentation at
-:gmt-docs:`legend.html#legend-codes`.
+symbols plotted using :meth:`pygmt.Figure.plot`. A legend entry is only added
+when the ``label`` parameter is used to state the desired text. Optionally,
+to adjust the legend, users can append different modifiers. A list of all
+available modifiers can be found at :gmt-docs:`gmt.html#l-full`. To create a
+multiple-column legend **+N** is used with the desired number of columns.
+For more complicated legends, users may want to write an ASCII file with
+instructions for the layout of the legend items and pass it to the ``spec``
+parameter of :meth:`pygmt.Figure.legend`. For details on how to set up such a
+file, please see the GMT documentation at :gmt-docs:`legend.html#legend-codes`.
 """
 
 # %%
+import numpy as np
 import pygmt
 
-fig = pygmt.Figure()
+# Set up some test data
+x = np.arange(-10, 10.2, 0.2)
+y1 = np.sin(x) + 1.1
+y2 = np.cos(x) + 1.1
+y3 = np.sin(x / 2) - 1.1
+y4 = np.cos(x / 2) - 1.1
 
-fig.basemap(projection="x2c", region=[0, 7, 3, 7], frame=True)
+# Create new Figure() object
+fig = pygmt.Figure()
 
-fig.plot(
-    data="@Table_5_11.txt",
-    style="c0.40c",
-    fill="lightgreen",
-    pen="faint",
-    label="Apples",
+fig.basemap(
+    projection="X10c/7c",
+    region=[-10, 10, -3.5, 3.5],
+    frame=["WSne", "xaf+lx", "ya1f0.5+ly"],
 )
-fig.plot(data="@Table_5_11.txt", pen="1.5p,gray", label="My lines")
-fig.plot(data="@Table_5_11.txt", style="t0.40c", fill="orange", label="Oranges")
 
+# -----------------------------------------------------------------------------
+# Top: Vertical legend (one column, default)
+
+# Use the label parameter to state the text label for the legend entry
+fig.plot(x=x, y=y1, pen="1p,green3", label="sin(x)+1.1")
+
+fig.plot(x=x, y=y2, style="c0.07c", fill="dodgerblue", label="cos(x)+1.1")
+
+# Add a legend to the plot; place it within the plot bounding box with both
+# reference ("J") and anchor ("+j") points being TopRight and with an offset
+# of 0.2 centimeters in x and y directions; surround the legend with a box
 fig.legend(position="JTR+jTR+o0.2c", box=True)
 
+# -----------------------------------------------------------------------------
+# Bottom: Horizontal legend (here two columns)
+
+# +N sets the number of columns corresponding to the given number, here 2
+fig.plot(x=x, y=y3, pen="1p,darkred,-", label="sin(x/2)-1.1+N2")
+
+fig.plot(x=x, y=y4, style="s0.07c", fill="orange", label="cos(x/2)-1.1")
+
+# For a multi-column legend, users have to provide the width via "+w", here it
+# is set to 6 centimeters; reference and anchor points are set to BottomRight
+fig.legend(position="JBR+jBR+o0.2c+w6c", box=True)
+
 fig.show()