surveydata (version 0.2.7)

Extract: Extract or replace subsets of surveydata, ensuring that the varlabels stay synchronized.

Description

The surveydata package makes it easy to extract specific questions from a surveydata object. Because survey data typically has question names like "Q1_a", "Q1_b", "Q1_c" the extract method for a surveydata object makes it easy to extract all columns by simply specifying "Q1" as the argument to the column index.

Usage

# S3 method for surveydata
[(x, i, j, drop = FALSE)
# S3 method for surveydata
[(x, i, j) <- value
# S3 method for surveydata
$(x, name) <- value

Arguments

x

surveydata object

i

row index

j

column index

drop

logical. Passed to [.data.frame. Note that the default is FALSE.

value

New value

name

Names of columns

Details

Extraction is similar to data frames, with three important exceptions:

• The column argument j is evaluated using which.q() and will return all columns where the column names match the pattern().

• The drop argument is FALSE. Thus the result will always be a surveydata object, even if only a single column is returned.

• All extraction methods retain the pattern and varlabels arguments.

See Also

surveydata-package, varlabels

Examples

names(membersurvey)
head(membersurvey["Q1"])
head(membersurvey[c("Q1", "Q2")])
head(membersurvey[membersurvey$Q2=="2009", c("Q1", "Q2")])

# The pattern is used to extract columns

pattern(membersurvey)

grep("Q20", names(membersurvey), value=TRUE)
head(membersurvey["Q20"])
head(membersurvey["Q20_other"])