Warning: “Variables with usage in documentation object ‘FANG’ but not in code:”

Question

On R-devel (>3.6.1 at the time), a new warning has popped up in my package when running R CMD Check that looks like:

“Variables with usage in documentation object ‘FANG’ but not in code:”
'FANG'

FANG is a data set that I include in my package.

You can see the exact error at: https://travis-ci.org/business-science/tibbletime/jobs/568639099#L3163

You can see the frozen state of this package at: https://github.com/business-science/tibbletime/blob/305e80ee3f6eecd728eb06937650dae03c94320c/R/data.R#L18

Below, I answer my own question about what this error means, and why it occurred.

Answer 1

This is a new check introduced in R-devel here: https://github.com/wch/r-source/commit/c9adb21c2e37cbc6dccd4c1eceec1873c10e3d9e#diff-4882a8c8e173bda109ed98da485e1428

While the error message is confusing, the fix for me was to set LazyData: true in my DESCRIPTION file.

The problem was that in my data.R file, I use roxygen2 to generate the Rd file. The data.R file looks like:

#' Stock prices for Facebook, Amazon, Netflix and Google from 2013-2016
#'
#' A dataset containing the date, open, high, low, close, volume, and adjusted
#' stock prices for Facebook, Amazon, Netflix and Google from 2013-2016.
#'
#' @format A tibble with 4,032 rows and 8 variables:
#' \describe{
#'   \item{symbol}{stock ticker symbol}
#'   \item{date}{trade date}
#'   \item{open}{stock price at the open of trading, in USD}
#'   \item{high}{stock price at the highest point during trading, in USD}
#'   \item{low}{stock price at the lowest point during trading, in USD}
#'   \item{close}{stock price at the close of trading, in USD}
#'   \item{volume}{number of shares traded}
#'   \item{adjusted}{stock price at the close of trading adjusted for stock splits, in USD}
#' }
#' @source \url{http://www.investopedia.com/terms/f/fang-stocks-fb-amzn.asp}
"FANG"

And the generated Rd looks like:

% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/data.R
\docType{data}
\name{FANG}
\alias{FANG}
\title{Stock prices for Facebook, Amazon, Netflix and Google from 2013-2016}
\format{A tibble with 4,032 rows and 8 variables:
\describe{
\item{symbol}{stock ticker symbol}
\item{date}{trade date}
\item{open}{stock price at the open of trading, in USD}
\item{high}{stock price at the highest point during trading, in USD}
\item{low}{stock price at the lowest point during trading, in USD}
\item{close}{stock price at the close of trading, in USD}
\item{volume}{number of shares traded}
\item{adjusted}{stock price at the close of trading adjusted for stock splits, in USD}
}}
\source{
\url{http://www.investopedia.com/terms/f/fang-stocks-fb-amzn.asp}
}
\usage{
FANG
}
\description{
A dataset containing the date, open, high, low, close, volume, and adjusted
stock prices for Facebook, Amazon, Netflix and Google from 2013-2016.
}
\keyword{datasets}

The issue is in the \usage{} section. I have LazyData: false implicitly, which means that \usage{FANG} is incorrect and should really be \usage{data(FANG)}. There is nothing that I could have changed in my data.R file to generate this, as roxygen2 essentially assumes you have LazyData: true when it generates the data Rd file.

So, this is a true error picked up by R CMD Check, but the message is a bit confusing. Luckily, the fix is fairly easy, and non-invasive.

Answer 2

I had the same Warning: “Variables with usage in documentation object ‘ ’ but not in code”. I solved as suggested also by John M. You just need to add in the data documentation in data.R the following tag: @usage

So in the example above it should be #' @usage data(FANG)