If you get an error message like following even if you have already installed an R package that has this function, you can check the following.
Error in geoMean(Value): could not find function "geoMean"
Open the “Manage R Package” dialog from inside of your project that you want to use the installed package.
Make sure the package you want to use is checked. If not checked, please check and click “OK” and try again.