Error: could not find function … in R

There are a few things you should check :

  1. Did you write the name of your function correctly? Names are case sensitive.
  2. Did you install the package that contains the function? install.packages("thePackage") (this only needs to be done once)
  3. Did you attach that package to the workspace ?
    require(thePackage) (and check its return value) or library(thePackage) (this should be done every time you start a new R session)
  4. Are you using an older R version where this function didn’t exist yet?
  5. Are you using a different version of the specific package? This could be in either direction: functions are added and removed over time, and it’s possible the code you’re referencing is expecting a newer or older version of the package than what you have installed.

If you’re not sure in which package that function is situated, you can do a few things.

  1. If you’re sure you installed and attached/loaded the right package, type"some.function") or ??some.function to get an information box that can tell you in which package it is contained.
  2. find and getAnywhere can also be used to locate functions.
  3. If you have no clue about the package, you can use findFn in the sos package as explained in this answer.
  4. RSiteSearch("some.function") or searching with rdocumentation or rseek are alternative ways to find the function.

Sometimes you need to use an older version of R, but run code created for a newer version. Newly added functions (eg hasName in R 3.4.0) won’t be found then. If you use an older R version and want to use a newer function, you can use the package backports to make such functions available. You also find a list of functions that need to be backported on the git repo of backports. Keep in mind that R versions older than R3.0.0 are incompatible with packages built for R3.0.0 and later versions.

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