27.15 Functions from Packages

20200105

R has a mechanism (called namespaces) for identifying the names of functions and variables from specific packages. There is no rule that says a package provided by one author can not use a function name already used by another package or by base R. Thus, functions from one package might overwrite the definition of a function with the same name from another package or from base R itself. A mechanism to ensure we are using the correct function is to prefix the function call with the name of the package providing the function, just like dplyr::mutate().

Generally in commentary we will use this notation to clearly identify the package which provides the function. In our interactive R usage and in scripts we tend not to use the namespace notation. It can clutter the code and arguably reduce its readability even though there is the benefit of clearly identifying where the function comes from.

For common packages we tend not to use namespaces but for less well-known packages a namespace at least on first usage provides valuable information. Also, when a package provides a function that has the same name as a function in another namespace, it is useful to explicitly supply the namespace prefix.

Preferred

library(dplyr)     # Data wranlging, mutate().
library(lubridate) # Dates and time, ymd_hm().
library(ggplot2)   # Visualize data.

ds <- get(dsname) %>%
  mutate(timestamp=ymd_hm(paste(date, time))) %>%
  ggplot(aes(timestamp, measure)) +
  geom_line() +
  geom_smooth()

Alternative

The use of the namespace prefix increases the verbosity of the presentation and that has a negative impact on the readability of the code. However it makes it very clear where each function comes from.

ds <- get(dsname) %>%
  dplyr::mutate(timestamp=
                  lubridate::ymd_hm(paste(date, time))) %>%
  ggplot2::ggplot(ggplot2::aes(timestamp, measure)) +
  ggplot2::geom_line() +
  ggplot2::geom_smooth()

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