Axis labels lost when use -RgXmin/Xmax/Ymin/Ymax to indicate a limited geographic domain.

[WXZhao7]

Description of the problem

Axis labels lost when use '-RgXmin/Xmax/Ymin/Ymax' to indicate a limited geographic domain.

Full code that generated the error

import pygmt

fig = pygmt.Figure()
region = "g0/10/0/10"
fig.basemap(
    region=region, projection="X5c", frame=["WSNE", "xaf+llon/deg", "yaf+llat/deg"]
    )
fig.show()

Full error message

PASTE ERROR MESSAGE HERE

System information

Please paste the output of python -c "import pygmt; pygmt.show_versions()":

PyGMT information:
  version: v0.4.1
System information:
  python: 3.9.7 | packaged by conda-forge | (default, Sep 29 2021, 19:20:46)  [GCC 9.4.0]
  executable: /home/wxz/Program/miniconda3/envs/seismic/bin/python
  machine: Linux-5.11.0-38-generic-x86_64-with-glibc2.31
Dependency information:
  numpy: 1.21.2
  pandas: 1.3.3
  xarray: 0.19.0
  netCDF4: 1.5.7
  packaging: 21.0
  ghostscript: 9.54.0
  gmt: 6.2.0
GMT library information:
  binary dir: /home/wxz/Program/miniconda3/envs/seismic/bin
  cores: 16
  grid layout: rows
  library path: /home/wxz/Program/miniconda3/envs/seismic/lib/libgmt.so
  padding: 2
  plugin dir: /home/wxz/Program/miniconda3/envs/seismic/lib/gmt/plugins
  share dir: /home/wxz/Program/miniconda3/envs/seismic/share/gmt
  version: 6.2.0

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[seisman]

@WXZhao7 This is expected behavior, because, for geographic maps, it's clear that the "X" axis is longitude and the "Y" axis is latitude, thus it makes little sense to label them.

[WXZhao7]

@WXZhao7 This is expected behavior, because, for geographic maps, it's clear that the "X" axis is longitude and the "Y" axis is latitude, thus it makes little sense to label them.

I just follow the GMT cookbook:

Geographic coordinates:
These are longitudes and latitudes and may be given in decimal degrees (e.g., -123.45417) or in the [±]ddd[:mm[:ss[.xxx]]][W|E|S|N] format (e.g., 123:27:15W). -Rg and -Rd are shorthands for “global domain” -R0/360/-90/90 and -R-180/180/-90/90 respectively.

When used in conjunction with the Cartesian Linear Transformation (-Jx or -JX) — which can be used to map floating point data, geographical coordinates, as well as time coordinates — it is prudent to indicate that you are using geographical coordinates in one of the following ways:

Use -Rg or -Rd to indicate the global domain.

Use -Rgxmin/xmax/ymin/ymax to indicate a limited geographic domain.

Add W, E, S, or N to the coordinate limits (e.g., -R15W/30E/10S/15N).

Alternatively, you may indicate geographical coordinates by supplying -fg; see Section Data type selection: The -f option.

My original idea is a pie wedge with r = 60deg and 0 < azimuth < 360. But I find that is difficult for pyGMT.

• Ver1: -SW can't recognize geographic distance r = 60deg

import pygmt

fig = pygmt.Figure()
region = "-60/60/-60/60"
fig.basemap(
    region=region, projection="X15c", frame=["WSNE", "xaf+llon/deg", "yaf+llat/deg"]
    )
fig.coast(
    borders=["1/0.5p,black"], shorelines="0.5p,black", land="lightgray",
    water="lightblue", resolution="l"
    )
fig.plot(x=0, y=0, style=f"W30/0/360", pen="2p,orange")
fig.show()

• Ver2: use geographic unit in style option: error near the boundary of longitude

import pygmt

fig = pygmt.Figure()
region = "0/360/-60/60"
fig.basemap(
    region=region, projection="X15c", frame=["WSNE", "xaf+llon/deg", "yaf+llat/deg"]
    )
fig.coast(
    borders=["1/0.5p,black"], shorelines="0.5p,black", land="lightgray",
    water="lightblue", resolution="l"
    )
fig.plot(x=180, y=0, style=f"W30d/0/360+w", pen="2p,orange")
fig.show()

• Ver3: use -RgXmin/Xmax/Ymin/Ymax to indicate a limited geographic domain: axis label lost

import pygmt

fig = pygmt.Figure()
region = "g0/360/-60/60"
fig.basemap(
    region=region, projection="X15c", frame=["WSNE", "xaf+llon/deg", "yaf+llat/deg"]
    )
fig.coast(
    borders=["1/0.5p,black"], shorelines="0.5p,black", land="lightgray",
    water="lightblue", resolution="l"
    )
fig.plot(x=180, y=0, style=f"W30d/0/360+w", pen="2p,orange")
fig.show()

Ver4: change to geographic projection: same as Ver1, and I find +r|+a in -Sw|W[+a|+r] can't work

import pygmt

fig = pygmt.Figure()
region = "0/360/-60/60"
fig.basemap(
    region=region, projection="M15c", frame=["WSNE", "xaf+llon/deg", "yaf+llat/deg"]
    )
fig.coast(
    borders=["1/0.5p,black"], shorelines="0.5p,black", land="lightgray",
    water="lightblue", resolution="l"
    )
fig.plot(x=180, y=0, style=f"W30d/0/350+r", pen="2p,orange")
fig.show()

[WXZhao7]

supplement
Ver4.

Ver5: use -RgXmin/Xmax/Ymin/Ymax in GMT6: axis label lost

#!/usr/bin/env -S bash -e
export GMT_SESSION_NAME=$$ # unique session name
gmt begin plot_-Sw pdf,png
gmt basemap -Rg0/360/-60/60 -JX15c -BWSNE -Bxaf+llon/deg -Byaf+llat/deg
gmt coast -Clightblue -Dl -Glightgray -N1 -W1 -Slightblue
gmt plot -SW30d+a << EOF
180 0 0 350
EOF
gmt end show

Ver6: use -RXmin/Xmax/Ymin/Ymax in GMT6

#!/usr/bin/env -S bash -e
export GMT_SESSION_NAME=$$ # unique session name
gmt begin plot_-Sw pdf,png
gmt basemap -R0/360/-60/60 -JX15c -BWSNE -Bxaf+llon/deg -Byaf+llat/deg
gmt coast -Clightblue -Dl -Glightgray -N1 -W1 -Slightblue
gmt plot -SW30d+a << EOF
180 0 0 350
EOF
gmt end show

I can't plot a pie properly :(

[weiji14]

Hi @WXZhao7, as mentioned in #1588 (comment), it isn't possible to label geographic axes in GMT/PyGMT. That said, you can try to use fig.text to put the annotations manually.

fig = pygmt.Figure()
region = "g0/360/-60/60"
fig.basemap(region=region, projection="X15c", frame=True)
fig.coast(
    borders=["1/0.5p,black"],
    shorelines="0.5p,black",
    land="lightgray",
    water="lightblue",
    resolution="l",
)
fig.text(position="BC", offset="0c/-1.2c", text="lon/deg", no_clip=True)
fig.text(position="LM", offset="-1.2c/0c", text="lat/deg", angle=90, no_clip=True)
fig.plot(x=180, y=0, style=f"W30d/0/360", pen="2p,orange")
fig.savefig("annotated_geo_map.png")
fig.show()

produces:

You might want to play around with the offset and font parameter to get the position and text size of the labels to look better. I'll close this issue now, but if you have other specific questions, feel free to ask them at https://forum.generic-mapping-tools.org/c/questions/pygmt-q-a/11.