# Global name 'mu' is not defined

**URL:** <https://get-help.theconstruct.ai/t/global-name-mu-is-not-defined/6457>\
**Category:** Kalman Filters\
**Tags:** error\
**Created:** [November 23, 2020, 11:49am UTC](https://get-help.theconstruct.ai/t/global-name-mu-is-not-defined/6457 "2020-11-23T11:49:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cls](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/c/e68b1a/32.png) [@cls](https://get-help.theconstruct.ai/u/cls)\
**Post date:** [November 23, 2020, 11:49am UTC](https://get-help.theconstruct.ai/t/global-name-mu-is-not-defined/6457/1 "2020-11-23T11:49:26Z")

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Hello,

When I try the commands in bellow:  
"Remember to have the launch file roslaunch kalman\_filter launch\_auxiliary\_nodes.launch running in WebShell #1, and the launch file roslaunch kalman\_filter kalman\_filter.launch executing in WebShell #2. "

I received so many of the following error:

[ERROR] [1606131916.463110, 767.128000]: bad callback: \<function odom\_callback at 0x7ff3ac4bbb18\>  
Traceback (most recent call last):  
File “/opt/ros/kinetic/lib/python2.7/dist-packages/rospy/topics.py”, line 750, in \_invoke\_callback  
cb(msg)  
File “/home/user/catkin\_ws/src/kalman\_filters\_files/kalman\_filter/scripts/kalman\_filter.py”, line 54, in odom\_callback  
filter\_pub.publish(mu)  
NameError: global name ‘mu’ is not defined

 ![Untitled](https://get-help.robotigniteacademy.com/uploads/default/original/2X/5/531a891858acd9e740bff72aa35fa7ea4b1ff379.png)

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<div class="post-metadata">

**Author:** ![albertoezquerro](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/albertoezquerro/32/7031_2.png) [@albertoezquerro](https://get-help.theconstruct.ai/u/albertoezquerro)\
**Post date:** [November 26, 2020, 8:52am UTC](https://get-help.theconstruct.ai/t/global-name-mu-is-not-defined/6457/2 "2020-11-26T08:52:55Z")

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Hello @cls,

You need to execute 1st:

`roslaunch kalman_filter launch_auxiliary_nodes.launch`

and 2nd:

`roslaunch kalman_filter kalman_filter_demo.launch`

Sorry for the confusion,