Pygmt pygmt.makecpt with dates / times

Q&A
1

Dear all,
I am struggling to make a colorscale with date in the format yyyy-mm-ddThh:mm:ss
I tried

pygmt.config(FORMAT_DATE_IN='yyyy-mm-dd')
pygmt.config(FORMAT_DATE_OUT='yyyy-mm-dd')

pygmt.makecpt(
    cmap='rainbow',
    series=['2021-01-01T','2021-03-01T'],
    output='date.cpt',
    verbose=True
    )

Things are not clear for me… I’ll appreciate if someone could help. That was quite easy with GMT6 !!
Thanks
cecile

2

Hi Cecile, Could you share the gmt command that you used for creating the colormap with dates/times? This would help for testing how to get the output equivalent. Thanks!

3

Hello
Actually, I realised that I always built the colorcale by hand. However, it could be great to build it using makecpt.
However, I was able to plot it with the correct dates:
gmt psscale -Cdate_coloscale.cpt -Dx18/4c+w-4c/0.3c+jTC -Bxaf+l"time" -R -J > $psfile_gen_time
with date_coloscale.cpt :
2009-11-26T 127 0 255 2010-03-01T 0 0 255
2010-03-01T 0 0 255 2010-06-01T 0 255 255
2010-06-01T 0 255 255 2010-09-01T 0 255 0
2010-09-01T 0 255 0 2010-12-01T 255 255 0
2010-12-01T 255 255 0 2011-03-06T 255 0 0
Many thanks
Cécile

4

Me again,
After using a colorscale made “by hand”, I am struggling again to plot the dots with a color consistent with the time (coltypes=“T”?).

fig.plot(
    x=lon,
    y=lat,
    style='c', 
    size=M,
    color=date_st,
    coltypes="T",
    pen='black',
    cmap=file_cpt_name
    )

Using GMT6, I used to write:
gmt psxy file_to_plot.xyt -R -V -W0.5 -Jm -Sc0.4 -C$file_cpt_name -fi2T > $psfile

Many thanks
Cécile

5

To be equivalent to the gmt command, you would use coltypes="i2T":

fig.plot(
x=lon,
y=lat,
style=‘c’,
size=M,
color=date_st,
coltypes=“i2T”,
pen="black",
cmap=file_cpt_name
)
6

The hand-made colormap is a discrete colormap. To create a discrete colormap using makecpt, the increment needs to be specified in the series argument (example below uses a 1 month increment):

import pygmt

pygmt.config(FORMAT_DATE_IN='yyyy-mm-dd')
pygmt.config(FORMAT_DATE_OUT='yyyy-mm-dd')

pygmt.makecpt(
    cmap='turbo',
    series=['2021-01-01T','2021-12-01T','1o'],
    output='date.cpt',
    verbose=True
    )
7

Dear Meghan,
I tried and it does not work.
I remain confused with the coltypes=“i2T”. With GMT it was related to the third column. In this case, how to know that it is related to ‘color’…
Sorry, but I am lost
Cécile