Annotating psrose beyond N,S,E,W

Q&A
1

GMT Users:

I’m trying to figure out how to add additional annotations for length, azimuth coordinates to a psrose plot. I’ve started out with a simple test plot,

gmt psrose rose_test.txt -A15.0 -D -R0/65/0/360 -JX10c -LW,E,S,N -W1.0p,blue -Bx20g5 -Byg30 -Gyellow -X2.0 -Y2.0 >& rose_test.ps

with the following rose_test.txt

5.0 0.0
10.0 30.0
15.0 60.0
20.0 90.0
25.0 120.0
30.0 150.0
35.0 180.0
40.0 210.0
45.0 240.0
50.0 270.0
55.0 300.0
60.0 330.0

This plots OK, but I’d like to add annotations to the plot. For example, azimuth coordinates for 30,60,120,150 degrees etc. But reading over the ver 6.2 doc page for psrose I’ don’t see anything other than the -L option for modifying graph labels.

I have tried to add test labels using a pstext call after psrose,

gmt pstext -A -R -JX -B -O << EOF >>& rose_test.ps
30.0 150.0 +a90+cCM+f30p,5,blue 0.0 CM 180
EOF

Screen Shot 2021-12-16 at 2.53.01 PM
Screen Shot 2021-12-16 at 2.53.01 PM1158×1106 188 KB

But I’m having some trouble understanding the new (ver 6.2) rules for pstext. Also, apparently pstext does not inherit the psrose polar coordinate system established by a previous psrose call.

Any help or advice would be appreciated.

2

The rose module is very old so there is some history here. You can certainly use basemap to overlay polar annotations, e.g.

basemap -R0/360/0/65 -JP10c -Bx20g5 -Byg30

but if you try you cannot use those -R -J combinations in the rose call. rose needs -R0/65/0/360 while the polar projection needs -R0/360/0/65. However, the overlay does work. I can look to see if we could band-aid prose to accept the polar cylindrical -JP with the corresponding -R for that projection.

As for text you are giving the modifiers to -F as part of the text so it is plotted as is. You want to use the -F option, say, -F+a90+cCM+f30p,5,blue, and then no CM in the data file. But looks like you are using +cCM to pick the center point AND also giving coordinates so there is a conflict here anyway.

Stick with the polar projection overlay above.

3

Paul:

Thanks a lot for that fix. I’ll give it a try.

Steve M.