Add a gallery example showing individual basic geometric symbols (#1211)

Co-authored-by: Meghan Jones <meghanj@alum.mit.edu>
Co-authored-by: Dongdong Tian <seisman.info@gmail.com>
Co-authored-by: Yao Jiayuan <coreman.seism@gmail.com>

examples/gallery/symbols/basic_symbols.py

@@ -0,0 +1,108 @@
+"""
+Basic geometric symbols
+-----------------------
+
+The :meth:`pygmt.Figure.plot` method can plot individual geometric symbols
+by passing the corresponding shortcuts to the ``style`` parameter. The 14 basic
+geometric symbols are shown underneath their corresponding shortcut codes.
+Four symbols (**-**, **+**, **x** and **y**) are line-symbols only for which we
+can adjust the linewidth via the ``pen`` parameter. The point symbol (**p**)
+only takes a color fill which we can define via the ``color`` parameter. For the
+remaining symbols we may define a linewidth as well as a color fill.
+
+"""
+
+import pygmt
+
+fig = pygmt.Figure()
+fig.basemap(region=[0, 8, 0, 3], projection="X12c/4c", frame=True)
+
+# define fontstlye for annotations
+font = "15p,Helvetica-Bold"
+
+# upper row
+y = 2
+
+# use a dash in x direction (-) with a size of 0.9 cm,
+# linewidth is set to 2p and the linecolor to "gray40"
+fig.plot(x=1, y=y, style="-0.9c", pen="2p,gray40")
+fig.text(x=1, y=y + 0.6, text="-", font=font)
+
+# use a plus (+) with a size of 0.9 cm,
+# linewidth is set to 2p and the linecolor to "gray40"
+fig.plot(x=2, y=y, style="+0.9c", pen="2p,gray40")
+fig.text(x=2, y=y + 0.6, text="+", font=font)
+
+# use a star (a) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" (default) and the
+# color fill to "darkorange"
+fig.plot(x=3, y=y, style="a0.9c", pen="1p,black", color="darkorange")
+fig.text(x=3, y=y + 0.6, text="a", font=font)
+
+# use a circle (c) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "darkred"
+fig.plot(x=4, y=y, style="c0.9c", pen="1p,black", color="darkred")
+fig.text(x=4, y=y + 0.6, text="c", font=font)
+
+# use a diamond (d) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "seagreen"
+fig.plot(x=5, y=y, style="d0.9c", pen="1p,black", color="seagreen")
+fig.text(x=5, y=y + 0.6, text="d", font=font)
+
+# use a octagon (g) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "dodgerblue4"
+fig.plot(x=6, y=y, style="g0.9c", pen="1p,black", color="dodgerblue4")
+fig.text(x=6, y=y + 0.6, text="g", font=font)
+
+# use a hexagon (h) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "lightgray"
+fig.plot(x=7, y=y, style="h0.9c", pen="1p,black", color="lightgray")
+fig.text(x=7, y=y + 0.6, text="h", font=font)
+
+# lower row
+y = 0.5
+
+# use an inverted triangle (i) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "tomato"
+fig.plot(x=1, y=y, style="i0.9c", pen="1p,black", color="tomato")
+fig.text(x=1, y=y + 0.6, text="i", font=font)
+
+# use pentagon (n) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "lightseagreen"
+fig.plot(x=2, y=y, style="n0.9c", pen="1p,black", color="lightseagreen")
+fig.text(x=2, y=y + 0.6, text="n", font=font)
+
+# use a point (p) with a size of 0.9 cm,
+# color fill is set to "lightseagreen"
+fig.plot(x=3, y=y, style="p0.9c", color="slateblue")
+fig.text(x=3, y=y + 0.6, text="p", font=font)
+
+# use square (s) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "gold2"
+fig.plot(x=4, y=y, style="s0.9c", pen="1p,black", color="gold2")
+fig.text(x=4, y=y + 0.6, text="s", font=font)
+
+# use triangle (t) with a size of 0.9 cm,
+# linewidth is set to 1p, the linecolor to "black" and the
+# color fill to "magenta4"
+fig.plot(x=5, y=y, style="t0.9c", pen="1p,black", color="magenta4")
+fig.text(x=5, y=y + 0.6, text="t", font=font)
+
+# use cross (x) with a size of 0.9 cm,
+# linewidth is set to 2p and the linecolor to "gray40"
+fig.plot(x=6, y=y, style="x0.9c", pen="2p,gray40")
+fig.text(x=6, y=y + 0.6, text="x", font=font)
+
+# use a dash in y direction (y) with a size of 0.9 cm,
+# linewidth is set to 2p and the linecolor to "gray40"
+fig.plot(x=7, y=y, style="y0.9c", pen="2p,gray40")
+fig.text(x=7, y=y + 0.6, text="y", font=font)
+
+fig.show()