# NOT RUN {
# first, create a data frame to be sorted...
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 )
# txt num1 num2 etc
# 1 bob 3 1 not
# 2 Clare 1 1 used
# 3 clare 2 3 as
# 4 bob 0 0 a
# 5 eve 0 3 sort
# 6 eve 2 2 term
#### Sorting by numeric variables ####
# Simplest use of the function is to sort the data frame by a single
# numeric variable, with the results to be returned in increasing
# order, and ties to be kept in their original order:
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
# Specifying a second sort term will break ties using the second
# term. For instance, we can sort by 'num1' (ascending order),
# breaking ties by 'num2' (ascending order):
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
# Specifying negative numbers sorts in descending order. For
# instance, to sort by 'num1' in descending order, but break
# ties by 'num2' in ascending order, use the following:
sortFrame( dataset, -num1, num2 )
# txt num1 num2 etc
# 1 bob 3 1 not
# 6 eve 2 2 term
# 3 clare 2 3 as
# 2 Clare 1 1 used
# 4 bob 0 0 a
# 5 eve 0 3 sort
#### Sorting by character variables ####
# When sorting by character variables (but not factors - see
# below), the default is to sort alphabetically, with upper
# case preceding lowr case. For example:
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
# Sorting into reverse alphabetical order is possible using
# minus signs. For example:
sortFrame( dataset, -txt )
# txt num1 num2 etc
# 5 eve 0 3 sort
# 6 eve 2 2 term
# 3 clare 2 3 as
# 2 Clare 1 1 used
# 1 bob 3 1 not
# 4 bob 0 0 a
#### Other examples #####
# If alphabetical order is not desired for character variables
# it is possible to force sortFrame to use the default 'ASCII'
# ordering, in which all upper case letters precede all lower
# case ones, by specifying alphabetical = FALSE, as follows:
sortFrame( dataset, txt, alphabetical = FALSE )
# txt num1 num2 etc
# 2 Clare 1 1 used
# 1 bob 3 1 not
# 4 bob 0 0 a
# 3 clare 2 3 as
# 5 eve 0 3 sort
# 6 eve 2 2 term
# Note that factors are treated differently to character vectors.
# They are not sorted alphabetically: instead they are sorted in
# factor level order. For example, if we construct a data frame in
# which 'txt' is a factor, the results follow the order of the levels
dataset2 <- dataset
dataset2$txt <- factor( dataset2$txt, levels = c('bob','eve','clare','Clare'))
sortFrame( dataset2, txt )
# txt num1 num2 etc
# 1 bob 3 1 not
# 4 bob 0 0 a
# 5 eve 0 3 sort
# 6 eve 2 2 term
# 3 clare 2 3 as
# 2 Clare 1 1 used
# Sorting by functions of multible variables is also possible.
# Note that this functionality is intended to be applied to numeric
# variables only. It does work for non-numeric variables because of
# the internal reliance on the xtfrm function, but the results may
# be unexpected.
sortFrame( dataset, num1+num2 )
# txt num1 num2 etc
# 4 bob 0 0 a
# 2 Clare 1 1 used
# 5 eve 0 3 sort
# 1 bob 3 1 not
# 6 eve 2 2 term
# 3 clare 2 3 as
# An example of a nonsensical application of mathematical operations
# when sorting by character vector. It works, since the character
# vector is treated as a numeric equivalent internally, but the
# output does not make a great deal of sense:
sortFrame( dataset, (txt-3)^2 )
# txt num1 num2 etc
# 2 Clare 1 1 used
# 3 clare 2 3 as
# 1 bob 3 1 not
# 4 bob 0 0 a
# 5 eve 0 3 sort
# 6 eve 2 2 term
# An example where sorting by text processing operations fails because
# the xtfrm function converts it to a numerical vector before the text
# processing operation is applied:
sortFrame( dataset, nchar(txt) )
# txt num1 num2 etc
# 1 bob 3 1 not
# 2 Clare 1 1 used
# 3 clare 2 3 as
# 4 bob 0 0 a
# 5 eve 0 3 sort
# 6 eve 2 2 term
# ... no sorting has occurred here. Future releases may allow "as is"
# terms to be included, which would allow something along the following
# lines: sortFrame( dataset, nchar(I(txt)) ), and would produce the
# desired output where the longer strings are sorted to the bottom of the
# data frame. However, no such functionality currently exists.
# }
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