Sorts a data frame using one or more variables.
sortFrame(x, ..., alphabetical = TRUE)Data frame to be sorted
A list of sort terms (see below)
Should character vectors be sorted alphabetically?
The sorted data frame
The simplest use of this function is to sort a data frame x
in terms of one or more of the variables it contains. If for instance,
the data frame x contains two variables a and b, then
the command sortFrame(x,a,b) sorts by variable a, breaking
ties using variable b. Numeric variables are sorted in ascending
order: to sort in descending order of a and then ascending order
of b, use the command sortFrame(x,-a,b). Factors are treated
as numeric variables, and are sorted by the internal codes (i.e., the first
factor level equals 1, the second factor levels equals 2 and so on).
Character vectors are sorted in alphabetical order, which differs from the
ordering used by the sort function; to use the default 'ascii'
ordering, specify alphabetical=FALSE. Minus signs can be used in
conjunction with character vectors in order to sort in reverse alphabetical
order. If c represents a character variable, then sortFrame(x,c)
sorts in alphabetical order, whereas sortFrame(x,-c) sorts in reverse
alphabetical order.
It is also possible to specify more complicated sort terms by including
expressions using multiple variables within a single term, but care is
required. For instance, it is possible to sort the data frame by the sum of
two variables, using the command sortFrame(x, a+b). For numeric
variables expressions of this kind should work in the expected manner, but
this is not always the case for non-numeric variables: sortFrame uses
the xtfrm function to provide, for every variable referred to
in the list of sort terms (...) a numeric vector that sorts in the
same order as the original variable. This reliance is what makes reverse
alphabetical order (e.g., sortFrame(x,-c)) work. However, it also
means that it is possible to specify somewhat nonsensical sort terms for
character vectors by abusing the numerical coding (e.g.
sortFrame(x,(c-3)^2); see the examples section). It also means
that sorting in terms of string operation functions (e.g., nchar)
do not work as expected. See examples section. Future versions of
sortFrame will (hopefully) address this, possibly by allowing the
user to "switch off" the internal use of xtfrm, or else by allowing
AsIs expressions to be used in sort terms.
txt <- c("bob","Clare","clare","bob","eve","eve")
num1 <- c(3,1,2,0,0,2)
num2 <- c(1,1,3,0,3,2)
etc <- c("not","used","as","a","sort","term")
dataset <- data.frame( txt, num1, num2, etc, stringsAsFactors=FALSE )
sortFrame( dataset, num1 )
#> txt num1 num2 etc
#> 4 bob 0 0 a
#> 5 eve 0 3 sort
#> 2 Clare 1 1 used
#> 3 clare 2 3 as
#> 6 eve 2 2 term
#> 1 bob 3 1 not
sortFrame( dataset, num1, num2 )
#> txt num1 num2 etc
#> 4 bob 0 0 a
#> 5 eve 0 3 sort
#> 2 Clare 1 1 used
#> 6 eve 2 2 term
#> 3 clare 2 3 as
#> 1 bob 3 1 not
sortFrame( dataset, txt )
#> txt num1 num2 etc
#> 1 bob 3 1 not
#> 4 bob 0 0 a
#> 2 Clare 1 1 used
#> 3 clare 2 3 as
#> 5 eve 0 3 sort
#> 6 eve 2 2 term