# LinearMap : error while running LinearMap

**URL:** <https://discourse.julialang.org/t/linearmap-error-while-running-linearmap/41966>\
**Category:** General Usage\
**Created:** [June 24, 2020, 7:00am UTC](https://discourse.julialang.org/t/linearmap-error-while-running-linearmap/41966 "2020-06-24T07:00:05Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![simeonschaub](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/simeonschaub/32/216566_2.png) [@simeonschaub](https://discourse.julialang.org/u/simeonschaub)\
**Post date:** [June 24, 2020, 8:00am UTC](https://discourse.julialang.org/t/linearmap-error-while-running-linearmap/41966/2 "2020-06-24T08:00:13Z")

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Please try to avoid posting screenshots and quote your code instead, as this makes it much easier to help you. Also try to make sure, you provide a complete working example, as you didn’t define `multiplyHPsi` anywhere. This thread may be helpful to you:

> [@Please read: make it easier to help you](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757):
>
> Welcome to the Julia Discourse! We are enthusiastic about helping Julia programmers, both beginner and experienced. This public service announcement (PSA) outlines best practices when asking for help. Following these points makes it easier for us to help you and more likely you’ll get a prompt, useful answer. Keywords are highlighted to make it easier to refer to specific points. Choose a descriptive title that captures the key part of your question, eg “plots with multiple axes” instead of …

That said, does your code work on a previous version of Julia? What version of `LinearMaps.jl` are you using? (You can find that out with `]st LinearMaps` in the REPL.)

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_[View the full topic](https://discourse.julialang.org/t/linearmap-error-while-running-linearmap/41966)._