# Trouble with mrmath **URL:** \ **Category:** Uncategorized\ **Created:** [October 7, 2020, 8:00am UTC](https://community.mrtrix.org/t/trouble-with-mrmath/4158 "2020-10-07T08:00:40Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![jdtournier](https://community.mrtrix.org/user_avatar/community.mrtrix.org/jdtournier/32/2594_2.png) [@jdtournier](https://community.mrtrix.org/u/jdtournier)\ **Post date:** [October 7, 2020, 8:14am UTC](https://community.mrtrix.org/t/trouble-with-mrmath/4158/2 "2020-10-07T08:14:05Z")
I think this might be related to the use of a long dash (–) instead of a regular dash (-) in the `–axis` option. This means the command doesn’t recognise `–axis` as an option, but treats it as a regular argument. When that happens, the command sees what it thinks are 5 regular arguments, and therefore assumes arguments 1, 2 & 3 are input images, argument 4 (`–axis`) is the operation to be performed, and the last argument (the number `5`) is the output image… Try using a regular dash rather than a long one. I think these issues tend to happen when commands are copy-pasted from documents that were written using MS Word, since it tends to ‘autocorrect’ dashes into long dashes quite routinely, it’s actually quite difficult to get it to stop… --- _[View the full topic](https://community.mrtrix.org/t/trouble-with-mrmath/4158)._