# Gmx angle during dPCA

**URL:** <https://gromacs.bioexcel.eu/t/gmx-angle-during-dpca/8894>\
**Category:** User discussions\
**Tags:** analysis-tools\
**Created:** [April 16, 2024, 7:31am UTC](https://gromacs.bioexcel.eu/t/gmx-angle-during-dpca/8894 "2024-04-16T07:31:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Karis](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@Karis](https://gromacs.bioexcel.eu/u/Karis)\
**Post date:** [April 16, 2024, 7:31am UTC](https://gromacs.bioexcel.eu/t/gmx-angle-during-dpca/8894/1 "2024-04-16T07:31:27Z")

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GROMACS version: 2023.3  
GROMACS modification: No  
I’ve been trying to run dPCA as outlined under the [manual](https://manual.gromacs.org/current/reference-manual/analysis/dihedral-pca.html) but on reaching the step for outputting the .trr file containing the sine cosine data, I receive the error:

Fatal error:  
Can not combine angles with trr dump

I’ve already seen 3 other posts ([1](https://gromacs.bioexcel.eu/t/fatal-error-cannot-combine-angles-with-trr-dump-gromacs/6213), [2](https://gromacs.bioexcel.eu/t/gmx-angle-fatal-error-can-not-combine-angles-with-trr-dump/6587), [3](https://gromacs.bioexcel.eu/t/gmx-angle-fatal-error/529)) on the error but so far no one seems to have an answer explaining the issue, so any help on this would be greatly appreciated

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**Author:** ![MagnusL](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/magnusl/32/2380_2.png) [@MagnusL](https://gromacs.bioexcel.eu/u/MagnusL)\
**Post date:** [April 16, 2024, 8:05am UTC](https://gromacs.bioexcel.eu/t/gmx-angle-during-dpca/8894/2 "2024-04-16T08:05:28Z")

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You need to specify that you are analyzing dihedral angles. You need to use the `-type dihedral` option to both `gmx mk_angndx` and `gmx angle`. For both tools, `angle` is the default.