Google Visualizations for Rails 3 - uninitialized constant ApplicationHelper::GoogleVisualization

I am using the following gem for Google Visualizations https://github.com/jeremyolliver/gvis

I have followed the instructions for installation and usage on the page but I get the following error:

uninitialized constant ApplicationHelper::GoogleVisualization

How can I correct this error? I think it may be to do with restarting the server or rails but I'm not sure how to do this

Also what is the common plugin/gem or approach to using Google Visualizations with rails 3?

EDIT: I have now rest开发者_如何学Pythonarted my server and get the same error. One thing I noticed in the installation instructions is renaming the directory:

mv vendor/plugins/rails/rails-google-visualization-plugin vendor/plugins/google_visualization

The first line has a sub directory called rails within vendor/plugins, however this is not actually created when the plugin is installed. I am not sure if this is a typo error or not in the installation instructions

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It's possible that you just need to restart your server. Open the console with your Mongrel or WEBrick running, and type Ctrl+C, and when it's done exiting, type rails s.