expand.bpairs {earth}  R Documentation 
Expand binomialpair data from short to long form
Description
Expand binomialpair data from “short” to “long” form.
The short form specifies the response with two columns giving the numbers of successes and failures. Example short form:
survived died dose sex 3 0 10 male 2 1 10 female 1 2 20 male 1 2 20 female
The long form specifies the response as single column of
TRUE
s and FALSE
s.
For example, the
long form of the above data (spaces and comments added):
survived dose sex TRUE 10 male # row 1 of short data: 0 died, 3 survived TRUE 10 male TRUE 10 male FALSE 10 female # row 2 of short data: 1 died, 2 survived TRUE 10 female TRUE 10 female FALSE 20 male # row 3 of short data: 2 died, 1 survived FALSE 20 male TRUE 20 male FALSE 20 female # row 4 of short data: 2 died, 1 survived FALSE 20 female TRUE 20 female
In this example the total number of survived and died for each row in the short data is the same, but in general that need not be true.
Usage
## S3 method for class 'formula'
expand.bpairs(formula = stop("no 'formula' argument"), data = NULL, sort = FALSE, ...)
## Default S3 method:
expand.bpairs(data = stop("no 'data' argument"), y = NULL, sort = FALSE, ...)
Arguments
formula 
Model formula such as 
data 
Matrix or dataframe containing the data. 
y 
Model response. One of:

sort 
Default 
... 
Unused, but provided for generic/method consistency. 
Value
A dataframe of the data in the long form, with expanded binomial pairs.
The first column of the data will be the response column
(a column of TRUE
s and FALSE
s).
Additionally, the returned value has two attached attributes:
bpairs.index
A vector of row indices into the returned data.
Can be used to reconstruct the short data from the long data
(although this package does not yet provide a function to do so).
ynames
Column names of the original response (a twoelement character vector).
Examples
survived < c(3,2,1,1) # short data for demo (too short to build a real model)
died < c(0,1,2,2)
dose < c(10,10,20,20)
sex < factor(c("male", "female", "male", "female"))
short.data < data.frame(survived, died, dose, sex)
expand.bpairs(survived + died ~ ., short.data) # returns long form of the data
# expand.bpairs(data=short.data, y=cbind(survived, died)) # equivalent
# expand.bpairs(short.data, c(1,2)) # equivalent
# expand.bpairs(short.data, c("survived", "died")) # equivalent
# For example models, see the earth vignette
# section "Short versus long binomial data".