Extract | R Documentation |
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.
## S3 method for class 'surveydata'
x[i, j, drop = FALSE]
## S3 replacement method for class 'surveydata'
x[i, j] <- value
## S3 replacement method for class 'surveydata'
x$name <- value
x |
surveydata object |
i |
row index |
j |
column index |
drop |
logical. Passed to |
value |
New value |
name |
Names of columns |
Extraction is similar to data frames, with three important exceptions:
The column argument j
is evaluated using which.q()
and will return all columns where the column names match the pattern()
.
The drop
argument is FALSE
. Thus the result will always be a surveydata object, even if only a single column is returned.
All extraction methods retain the pattern
and varlabels
arguments.
surveydata-package, varlabels
names(membersurvey)
head(membersurvey["Q1"])
head(membersurvey[c("Q1", "Q2")])
head(membersurvey[membersurvey$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"])
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