# Customized annotation for colorbar - PyGMT **URL:** \ **Category:** PyGMT Q&A\ **Created:** [April 27, 2023, 1:12am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892 "2023-04-27T01:12:12Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![sfpoveda](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/sfpoveda/32/3066_2.png) [@sfpoveda](https://forum.generic-mapping-tools.org/u/sfpoveda)\ **Post date:** [April 27, 2023, 1:12am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/1 "2023-04-27T01:12:12Z")
Hi, I’ve tried to make a colorbar with customized annotations (irregular intervals) in PyGMT, but all attempts failed. I want to generate a colorbar like this: ![image](https://canada1.discourse-cdn.com/flex047/uploads/gmt/original/2X/7/7c89fffdfebc336b36fea3b3d93936c737c79820.png) But I do not know how to modify the code so that I get those results. This is my code. I’d appreciate any help! ![image](https://canada1.discourse-cdn.com/flex047/uploads/gmt/original/2X/b/b8adca07d0c09a1e9f9972ae9c2c5a8029ace32b.png) ---
**Author:** ![seisman](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/seisman/32/4_2.png) [@seisman](https://forum.generic-mapping-tools.org/u/seisman)\ **Post date:** [April 27, 2023, 1:31am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/2 "2023-04-27T01:31:51Z")
Does changing your `f'a{100}'` to `"a"` works? ---
**Author:** ![sfpoveda](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/sfpoveda/32/3066_2.png) [@sfpoveda](https://forum.generic-mapping-tools.org/u/sfpoveda)\ **Post date:** [April 27, 2023, 1:46am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/3 "2023-04-27T01:46:59Z")
Yep, f’a{100}’ works the same as a100. But I do not think this is the problem. The real problem is that PyGMT only allows me to plot a regular interval in the annotations (for the case of a100 that would be 0, 100, 200, 300, …, 800) and instead I need an irregular interval (0, 30, 70, 300, 500, 800). When trying with only “a” instead of “a100”, a regular interval continues appearing ---
**Author:** ![yvonnefroehlich](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/yvonnefroehlich/32/5064_2.png) [@yvonnefroehlich](https://forum.generic-mapping-tools.org/u/yvonnefroehlich)\ **Post date:** [April 27, 2023, 9:41am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/4 "2023-04-27T09:41:29Z")
Hello @sfpoveda, welcome to the GMT forum! So far, I can only provide a workaround to accomplish colorbar annotations based on the (irregular) values in a personal colormap. Calling the `pygmt.Figure.colorbar` method twice may work here, even it is not elegant or really satisfying. _Code example_: ```auto import pygmt fig = pygmt.Figure() # Set up a personal (un-equal) colormap pygmt.makecpt( cmap="red,yellow,green,purple,blue", series="0,30,70,300,500,800", reverse=False, ) fig.basemap( region=[0, 10, 0, 3], projection="X10c/3c", frame=True, ) # Workaround: Call colorbar method twice # First # Add x label via the frame parameter fig.colorbar( # Annotation (a) step must be larger than highest value in the colormap, # as then no annotations are visible # Set tick (f) step to 100 # Add label (+l) frame=["xa801f100+lProfundidad in km"], ) # Second # Use defaults of frame parameter # Then the annotations match the intervals of the personal colormap fig.colorbar() fig.show() # fig.savefig(fname="unequal_cb.png") ``` _Output figure_: ![unequal_cb](https://canada1.discourse-cdn.com/flex047/uploads/gmt/original/2X/5/56996436bfea453907c552fda26037a85591f4a5.png) * * * For next time posting, please provide your code not in form of a screen shot, but just copy and past it. Then people can simply cope it, which makes it easier to help you 🙂. You can format your script as code by placing three backticks in the line before and after the block with the script: ````auto ``` your script formated as code ``` ```` ---
**Author:** ![seisman](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/seisman/32/4_2.png) [@seisman](https://forum.generic-mapping-tools.org/u/seisman)\ **Post date:** [April 27, 2023, 10:05am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/5 "2023-04-27T10:05:12Z")
It seems it’s impossible to use the default annotations but also add a label to a colorbar. Here is a minimal bash script to reproduce it: ```auto gmt begin map gmt makecpt -Cred,yellow,green,purple,blue -T0,30,70,300,500,800 gmt colorbar -Dx0c/0c+w10c+h -B+l"X label" gmt end show ``` Ping @pwessel ---
**Author:** ![pwessel](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/pwessel/32/30_2.png) [@pwessel](https://forum.generic-mapping-tools.org/u/pwessel)\ **Post date:** [April 27, 2023, 10:35am UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/6 "2023-04-27T10:35:56Z")
Seems true. I recommend using the y-label to set units or whatever should apply to the cpt axis. ---
**Author:** ![sfpoveda](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/sfpoveda/32/3066_2.png) [@sfpoveda](https://forum.generic-mapping-tools.org/u/sfpoveda)\ **Post date:** [April 27, 2023, 3:37pm UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/7 "2023-04-27T15:37:30Z")
Thanks! ---
**Author:** ![yvonnefroehlich](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/yvonnefroehlich/32/5064_2.png) [@yvonnefroehlich](https://forum.generic-mapping-tools.org/u/yvonnefroehlich)\ **Post date:** [April 28, 2023, 12:38pm UTC](https://forum.generic-mapping-tools.org/t/customized-annotation-for-colorbar-pygmt/3892/8 "2023-04-28T12:38:35Z")
Thanks! For units and not too long labels this is a good idea.