Add categorical colorbars for plot and plot3d gallery examples

[michaelgrund]

Description of the problem

I recognized that some colors of individual gallery examples produced with 6.2.0rc1 show deviations compared to the versions generated with 6.1 (see below). Any ideas what's the reason for that?

6.1 versions

6.2.0rc1 versions

[seisman]

The generated CPTs are different. I think there were some CPT-related changes in upstream GMT. The one generated by GMT 6.2.0rc1 makes more sense to me.

GMT 6.1.1:

$ gmt makecpt -Cinferno -T0/3/1 -F+c
0	50.998/10/94.499	L
1	187/54.5/84.5	L
2	251.5/181/25.002	B
B	black
F	white
N	127.5

GMT 6.2.0rc1:

$ gmt makecpt -Cinferno -T0/3/1 -F+c
0	32.75/12/73.75	L
1	137.25/34/106	L
2	227.37/89.375/50.25	L
3	249/201.25/50.375	B
N	128

[maxrjones]

Yes, the previous CPT range was considered a bug that was fixed in this PR: GenericMappingTools/gmt#4446. I think we should update the series settings for makecpt accordingly in the examples.

[seisman]

I think we should update the series settings for makecpt accordingly in the examples.

I agree. I think we also need to add a colorbar to these examples. We didn't do that before, because GMT 6.1.1 has some bugs/limitations when plotting categorical colorbars, which should be fixed in GMT 6.2.0rc1.

[maxrjones]

I think we should update the series settings for makecpt accordingly in the examples.

I agree. I think we also need to add a colorbar to these examples. We didn't do that before, because GMT 6.1.1 has some bugs/limitations when plotting categorical colorbars, which should be fixed in GMT 6.2.0rc1.

Agreed. Are you interested in updating the examples @michaelgrund? I can submit a PR if you are not interested or do not have time.

[michaelgrund]

I think we should update the series settings for makecpt accordingly in the examples.

I agree. I think we also need to add a colorbar to these examples. We didn't do that before, because GMT 6.1.1 has some bugs/limitations when plotting categorical colorbars, which should be fixed in GMT 6.2.0rc1.

Agreed. Are you interested in updating the examples @michaelgrund? I can submit a PR if you are not interested or do not have time.

I will work on that the upcoming weekend and will open a corresponding PR @meghanrjones.