rEHR (version 1.0)

first_events: Selects the earliest event grouped by patient

Description

This function runs a select_events() query and then groups by patient id and picks only the earliest event for each patient

Usage

first_events(db = NULL, tab, columns = "eventdate", where = NULL, sql_only = FALSE, group_column = "patid", date_column = "eventdate")

Arguments

db

A database connection object

tab

the database table to extract from

columns

The other columns to be extracted

where

sting representation of the selection criteria

sql_only

logical should the function just return a string of the SQL query?

group_column

column to group by. Default is patid

date_column

the column to sort by. default is eventdate

Value

a dataframe or a string representing an sql query

Examples

## Not run: 
# b1 <- first_events(db, tab = "Clinical", columns = c("eventdate", "medcode"), 
# where = "medcode %in% .(a$medcode)")
# first_events(tab = "Clinical", columns = c("eventdate", "medcode"), 
# where = "medcode %in% c(1, 2, 3, 4)", sql_only = TRUE)
# ## End(Not run)