Bug with velo example in gmt 6.1.1

[lhoupert]

Description of the problem

I am currently working in implementing the velo function in pygmt.

I just realised that, since gmt 6.1.1, the first example at the end of the velo is not giving the same output than in the previous gmt version. Particularly, the current scaling options don't match anymore the description the example:

The following should make big red arrows with green ellipses, outlined in red. Note that the 39% confidence scaling will give an ellipse which fits inside a rectangle of dimension Esig by Nsig

Full script that generated the error

gmt velo << END -R-10/10/-10/10 -W0.25p,red -Ggreen -L -Se0.2i/0.39+f18p -B1g1 -Jx0.4/0.4 -A1c+p3p+e -V -pdf test
#Long. Lat. Evel Nvel Esig Nsig CorEN SITE
#(deg) (deg) (mm/yr) (mm/yr)
0. -8. 0.0 0.0 4.0 6.0 0.500 4x6
-8. 5. 3.0 3.0 0.0 0.0 0.500 3x3
0. 0. 4.0 6.0 4.0 6.0 0.500
-5. -5. 6.0 4.0 6.0 4.0 0.500 6x4
5. 0. -6.0 4.0 6.0 4.0 -0.500 -6x4
0. -5. 6.0 -4.0 6.0 4.0 -0.500 6x-4
END

Actual outcome

Expected outcome

The expected outcome should be something similar to the figure below:

System information

• Operating system: ProductName: Mac OS X ProductVersion: 10.15.7 BuildVersion: 19H2
• GMT version (gmt --version): 6.1.1

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[seisman]

I just tried the example using GMT 6.1.1, 6.1.0, 6.0.0 and 5.4.5. They all gives me the same results (the Actual outcome above). So it seems velo has some incompatible change before GMT 5.4.

[seisman]

I think this is a problem of the velo example, not a velo bug, and #4426 is a good fix to the velo example.

@PaulWessel Agree?

[PaulWessel]

Yep, seems fine.

[seisman]

Closed by #4426.