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Select only distinct columns

Source: R/helpers.R
select_distinct.Rd

Select all columns that has only one level for a given grouping scope. Useful when dealing with mixed datasets containing both long data and repeated short data.

Usage

select_distinct(df, .by)

Arguments

df

a dataframe

.by

optional grouping columns

Value

df with less columns

Examples

db = edc_example()
#> Warning: Option "edc_lookup" has been overwritten.
db$ae %>% colnames()
#> [1] "subjid"  "crfname" "aesoc"   "aegr"    "n_ae"    "sae"    
#`crfname` has one level for the whole dataset
db$ae %>% select_distinct() %>% colnames()
#> [1] "crfname"
#`n_ae` has one level per patient
db$ae %>% select_distinct(.by=subjid) %>% colnames()
#> [1] "subjid"  "crfname" "n_ae"