first_events: Selects the earliest event grouped by patient

In rEHR: Manipulating and Analysing Electronic Health Record Data

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)

rEHR documentation built on Jan. 23, 2017, 1 p.m.