## Scaling question

Dear GMT people,

I would like to plot the largest container ports with circles scaled for tonnage. So I've prepared this data file (Shanghai, Singapore, Shenzhen, ..):

```122.07    30.62    36537000
103.75    1.27    30922300
113.87    22.48    24204000
121.83    29.93    20620000
```

The psxy manpages simply states To plot the xyz values in the file quakes.xyzm as circles with size given by the magnitude [..] using the CPT rgb.cpt on a linear map, use

`gmt psxy quakes.xyzm -R0/1000/0/1000 -JX6i -Sc -Crgb -B200 > map.ps"`

But sadly I'm a bloody noob and just don't get it replicated. Here is my source code:

```ps=example.ps
proj=Kf0
scale=9i
center=45g30
gmt set FONT_ANNOT_PRIMARY 10p FONT_TITLE 18p

pscoast -Rg -J\$proj/\$scale -B\$center -B+t"Largest container ports worldwide" \
-Gwheat -Slightblue \
-Dc -A2000 -K -Y2.75i > \$ps
psxy ports.xyz -Rg -J\$proj/\$scale -Sc -O -K >> \$ps
ps2pdf example.ps example.pdf
```

Thanks in advance for any help.

### Replies (5)

#### RE: Scaling question - Added by Paul24 days ago

Your tonnage makes for poor symbol diameters (e.g., 36537000 cm) so you probably want to scale them to something reasonable. For instance, a scale of 1e-8 would change 36537000 to 0.365 cm. So run psxy as you do but tell it to get the first 3 columns but scale the third column accordingly: -i0,1,2+s1e-8

#### RE: Scaling question - Added by Engelbert12 days ago

Thank you very much. In the moment I'm fighting with GDAL ("ERROR 1: GMT driver has no vector capabilities."), but this is not your department.

#### RE: Scaling question - Added by Andreas12 days ago

I think they changed the OGR/GMT driver name from GMT to OGR_GMT in a (recent) version.

#### RE: Scaling question - Added by Engelbert10 days ago

Thanks for the OGR_GMT hint.

```psxy CN.gmt -Rg -J\$proj/\$scale -A -O -K >> \$ps
```

works well for plotting some lines. But how do I change the color and line thickness?

#### RE: Scaling question - Added by Andreas10 days ago

Change color and thickness with -W.

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