Error: could not find function … in R

Question

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I am using R and tried some.function but I got following error message:

Error: could not find function "some.function"

This question comes up very regularly. When you get this type of error in R, how can you solve it?

Answer 1

If this occurs while you check your package (R CMD check), take a look at your NAMESPACE.

You can solve this by adding the following statement to the NAMESPACE:

exportPattern("^[^\\\\.]")

This exports everything that doesn't start with a dot ("."). This allows you to have your hidden functions, starting with a dot:

.myHiddenFunction <- function(x) cat("my hidden function")

Answer 2

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) 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?

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 help.search("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 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.

Answer 3

This error can occur even if the name of the function is valid if some mandatory arguments are missing (i.e you did not provide enough arguments).
I got this in an Rcpp context, where I wrote a C++ function with optionnal arguments, and did not provided those arguments in R. It appeared that optionnal arguments from the C++ were seen as mandatory by R. As a result, R could not find a matching function for the correct name but an incorrect number of arguments.

Rcpp Function : SEXP RcppFunction(arg1, arg2=0) {}
R Calls :
RcppFunction(0) raises the error
RcppFunction(0, 0) does not

Answer 4

Rdocumentation.org has a very handy search function that - among other things - lets you find functions - from all the packages on CRAN, as well as from packages from Bioconductor and GitHub.

Answer 5

I had the error

Error: could not find function some.function

happen when doing R CMD check of a package I was making with RStudio. I found adding

exportPattern(".")

to the NAMESPACE file did the trick. As a sidenote, I had initially configured RStudio to use ROxygen to make the documentation -- and selected the configuration where ROxygen would write my NAMESPACE file for me, which kept erasing my edits. So, in my instance I unchecked NAMESPACE from the Roxygen configuration and added exportPattern(".") to NAMESPACE to solve this error.

Answer 6

You may be able to fix this error by name spacing :: the function call

comparison.cloud(colors = c("red", "green"), max.words = 100)

to

wordcloud::comparison.cloud(colors = c("red", "green"), max.words = 100)