This function extracts the cohort ID (e.g., SAB) from the subject ID
(e.g., SubjectID). By default it takes the first three characters.
extract_cohort(dat, id_var, st, en)
Arguments
- dat
A dataframe containing the variables of interest. A dataframe.
- id_var
The variable name to be used to identify subjects. A string.
- st
Integer indicating the first element to be extracted. An integer.
- en
Integer indicating the last element to be extracted. An integer.
Value
A dataframe containing a new column named cohort. A dataframe.