The goal of naidem is to compute the median in a way that handles
missing values properly: returning NA if and only if the median can’t
be determined from the data. Its source code has no dependencies.
Use median2() as a drop-in replacement for median(). It is the same
as in median() by default, except for handling missing values.
You can install the development version of naidem like so:
remotes::install_github("lhdjung/naidem")library(naidem)Why and how to use naidem:
Base R’s median() function returns NA whenever the input vector
contains one or more NAs. In many cases, missing values do make it
impossible to compute the median. Yet some distributions have a clear
median even so:
x1 <- c(6, 7, 7, 7, NA)
median(x1)
#> [1] NAThe actual median is 7, irrespective of the true value behind NA.
Use naidem’s median2() instead. This function will return the median
whenever it can be determined:
median2(x1)
#> [1] 7If the median really is unclear, both functions return NA:
x2 <- c(3, 4, 4, 5, NA, NA)
median(x2)
#> [1] NA
median2(x2)
#> [1] NACompare this to NA^0, which returns 1 even though NA^2 returns
NA. If the exponent is 0, the result is the same for all possible
bases. The same is sometimes true for the median. Therefore,
implementations should check for this case and return the median if and
only if it can be determined. This also makes NA more meaningful when
it is returned: users can be sure that the median really is unknown.
See Implementing the algorithm for more information on naidem’s solution.
What to do if the median really is unknown, like above? median_range()
will attempt to narrow it down to its minimal and maximal possible
medians:
median_range(x2)
#> [1] 3.5 4.5“naidem” is “median” backwards, but it also expresses the goal of
treating NA in the same (idem) conceptual way as R language
primitives like ^ do. Note that naidem is not about imputation at all,
but simply about determining the median.
The moder package serves a similar purpose, but for the mode instead of the median. Working on moder provided the impetus behind naidem.