recoder (version 0.1.2)

recoder: Simple and Handy Recoder

Description

A flexible function for recoding a variable. It can be used for anything from simple explicit recoding to piecewise-defined transformations.

Usage

recoder(var, recode, other = NULL, na = NA, as.what = NULL)

Value

The recoded vector is returned.

Arguments

var

var is a variable (vector) being recoded.

recode

recode contains the instructions for how the recoding is done. Each instruction is in the form of condition: newvalue and instrunctions must be separated by semicolons (;).

other

When other=NULL, elements that do not satisfy any of the coditions in the instructions given by recode will by defaul remain unchanger, otherwise they will be changed to other

na

When na=NULL, NA values will not be changed in the vector, otherwise, they will be changed to na.

as.what

if as.what is specified, the final vector is forced to be of the given type. For example, it will be made a factor if as.what= "factor" is specified.

Author

Ali Sanaei

Details

recode contains the instructions for how the recoding is done. Each instruction is in the form of condition: newvalue and instrunctions must be separated by semicolons (;). E.g., 1:2; 2:-1; 3:0 will change all ones to two, twos to negative one, and threes to zero. Instruction can include compound conditions and functions for newvalue expressed in terms of $. For example, "<0:0; >2:4; >=0 & <=2 : $^2" will give zero for all the values below 0, 4 for all the values above 2, and squared values for anything between 0 and 2.

The input can be other types beside numeric. For characters and factors, it is important that the form "old":"new" includes quotations around both the left-hand side and the right-hand side.

When the input is a factor, recoding works as expected, but new levels cannot be assigned. In order to assign new levels, the input vector should be made into something else (e.g., a character) and then the argument as.what could be set to "factor" to get a factor as the end result.

See Also

cut, recode

Examples

u = rnorm(1000)
u.2 = recoder(u,'<-2: -2; >2 : 2' ,other = 0)
plot(u,u.2)

# use a function of 'x' for assigning new values based on old values
u.3 = recoder(u,'<-2: -2; >2 : 2; >=-2 & <=2 : $^3/4') 
# NOTE: instructions in recode are executed from left to right
# So u.3 and u.4 are the same
u.4 = recoder(u,'<-2: -2; >=-2 : $^3/4;  >2 : 2')
plot(u, u.3)

# another example of a piecewise defined function
x = runif(1000,-1,10)
y = recoder(x,'>0 & <1: sqrt($); >=1 : 1+log($)' ,other=NA) 
plot(y~x)
table(is.na(y))

# we can also create other types of variables
k = rpois(n = 10000, lambda = 3)
evodd = recoder(k %% 2, '0: "even"; 1: "odd" ')
table(evodd)

# the output could also be made a factor, etc., using "as.what" argument
evodd.factor = recoder(k %% 2, '0: "even"; 1: "odd" ', as.what='factor')

# characters are recoded similarly
str = c('a','b','x','z',NA) 
str2 = recoder(str, '"x":"c"; "z":"d" ')
str3 = recoder(str, '"a":1; "b":2; "x":3; "z":4 ')
print(str3) #note that this is still not numeric
num3 = recoder(str, '"a":1; "b":2; "x":3; "z":4 ', as.what='numeric')
print(num3)

# when input is a factor, the levels are fixed
f1 = factor( c('a','b','x','z',NA)  )
f2 = recoder( f1, '"x":"a"; "z":"b" ')

## The following line causes an issue
## because "c" and "d" are not recognized 
## as existing labels.
#  f3 = recoder(f1, '"x":"c"; "z":"d" ') 
# The proper way to do it is to first turn f1 
# into a character vector and then recode it.
f3 = recoder( as.character(f1), '"x":"c"; "z":"d" ' , as.what= "factor")