# Two color cpt at -1 and +1 with no centre value **URL:** \ **Category:** Q&A\ **Created:** [November 11, 2020, 5:12am UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025 "2020-11-11T05:12:28Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![weiji14](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/weiji14/32/33_2.png) [@weiji14](https://forum.generic-mapping-tools.org/u/weiji14)\ **Post date:** [November 11, 2020, 5:12am UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/1 "2020-11-11T05:12:28Z")
I’m trying to make a two color categorical CPT using [`makecpt`](https://docs.generic-mapping-tools.org/dev/makecpt.html#t), with values at exactly -1 and +1, but can’t seem to get it right. This is with GMT version [`6.2.0_92c5676_2020.11.10`](https://github.com/conda-forge/gmt-feedstock/pull/110). ```bash $ gmt makecpt -Cberlin -T-1/1/2 -F+cNegative,Positive -1 24.5/12/9.5 B ;Negative N white ``` ```bash $ gmt makecpt -Cberlin -T-1/1/1 -F+cNegative,Positive -1 40.25/104.25/134.5 L ;Negative 0 123.5/50.5/28.5 B ;Positive N white ``` ```bash $ gmt makecpt -Cberlin -T-1/1/0.5 -F+cNegative,Positive -1 81.375/159.12/211.25 L ;Negative -0.5 20/48.75/62.75 L ;Positive 0 63.75/18/1 L 0.5 188.25/109.25/97.25 B N white ``` ```bash $ gmt makecpt -Cberlin -T-1/2/1 -F+cNegative,Positive -1 61/143/186.5 L ;Negative 0 24.5/12/9.5 L ;Positive 1 167/89.5/73 B N white ``` ### Desired output How to create a CPT with just two colors (e.g. red and blue) and no centre value (0)? ```bash -1 40.25/104.25/134.5 L ;Negative 1 123.5/50.5/28.5 B ;Positive N white ``` ---
**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:** [November 11, 2020, 5:32am UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/2 "2020-11-11T05:32:48Z")
Probably not obvious, but ``` gmt makecpt -Cberlin -T-1/3/2 -F+cNegative,Positive -1 40.25/104.25/134.5 L ;Negative 1 123.5/50.5/28.5 B ;Positive N white ``` ---
**Author:** ![weiji14](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/weiji14/32/33_2.png) [@weiji14](https://forum.generic-mapping-tools.org/u/weiji14)\ **Post date:** [November 11, 2020, 9:27am UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/3 "2020-11-11T09:27:28Z")
Ah right, just needed one more to get to 3! Thanks! While we’re on the CPT theme, how does the soft hinge work? I’m getting a warning when trying to set it. ```bash gmt makecpt -Cberlin+h3 -T-1/7/2 makecpt [WARNING]: gmt_stretch_cpt: CPT says it has a hinge but none is actually found? - ignored. -1 81.375/159.12/211.25 1 81.375/159.12/211.25 L 1 20/48.75/62.75 3 20/48.75/62.75 L 3 63.75/18/1 5 63.75/18/1 L 5 188.25/109.25/97.25 7 188.25/109.25/97.25 B B 158/176/255 F 255/173/173 N white ``` Using `+h1`, `+h0` or `+h3` gives me the same result, but that doesn’t seem right. ---
**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:** [November 11, 2020, 8:23pm UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/4 "2020-11-11T20:23:30Z")
If the CPT has a soft hinge you can turn it into a hard hinge via +h. The list of CPTs in the docs indicates which ones has soft hinges - berlin does not. ---
**Author:** ![weiji14](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/weiji14/32/33_2.png) [@weiji14](https://forum.generic-mapping-tools.org/u/weiji14)\ **Post date:** [November 11, 2020, 8:36pm UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/5 "2020-11-11T20:36:42Z")
Hmm, doesn’t the white triangle indicate a soft hinge? Copied from [https://docs.generic-mapping-tools.org/dev/cookbook/cpts.html#id3:](https://docs.generic-mapping-tools.org/dev/cookbook/cpts.html#id3:) ![image](https://canada1.discourse-cdn.com/flex047/uploads/gmt/original/1X/5f67d6f9b0979c35c0360b9612e2cc4e988c0745.png) ---
**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:** [November 11, 2020, 8:43pm UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/6 "2020-11-11T20:43:55Z")
I will look at the hinge message - perhaps not checking correctly. BTW, the original issues with -T will be fixed - I am declaring that a bug; should not have to say -T-1/3/2 to get -1, +1… ---
**Author:** ![Joaquim](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/joaquim/32/16_2.png) [@Joaquim](https://forum.generic-mapping-tools.org/u/Joaquim)\ **Post date:** [November 11, 2020, 9:16pm UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/7 "2020-11-11T21:16:47Z")
And **-T-1,1** should work too ```auto gmt makecpt -Cberlin -T-1,1 -F+c -1 24.5/12/9.5 B B 158/176/255 F 255/173/173 N white ``` ---
**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:** [November 11, 2020, 9:27pm UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/8 "2020-11-11T21:27:53Z")
Yes. I will fix that too. ---
**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:** [November 11, 2020, 11:10pm UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/9 "2020-11-11T23:10:15Z")
Problem with the hinge is that a z = 0.0 entry is missing in several of the SCM CPTs. I need to add the same processing I do for oleron. ---
**Author:** ![weiji14](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/weiji14/32/33_2.png) [@weiji14](https://forum.generic-mapping-tools.org/u/weiji14)\ **Post date:** [November 13, 2020, 2:10am UTC](https://forum.generic-mapping-tools.org/t/two-color-cpt-at-1-and-1-with-no-centre-value/1025/10 "2020-11-13T02:10:01Z")
Cool, the original problem with the unintuitive `makecpt -T-1/3/2` should be fixed (soon) in [https://github.com/GenericMappingTools/gmt/pull/4446](https://github.com/GenericMappingTools/gmt/pull/4446), and the colormap hinge problem is fixed already in [https://github.com/GenericMappingTools/gmt/pull/4447](https://github.com/GenericMappingTools/gmt/pull/4447)! Thanks for the quick work!