R and approximate match in the column's name

Question

I notice that sometimes R uses approximate match when I manipulate a column.

Example

age=18:19
height=c(76.1,77)
village=data.frame(age=age,height=he         


        

Answer 1

You can use [

> village["ag"]
Fehler in `[.data.frame`(village, "ag") : undefined columns selected

> village["age"]
  age
1  18
2  19

The function [[ allows both approaches (argument exact):

> village[["ag"]]
NULL

> village[["age"]]
[1] 18 19

> village[["ag", exact = FALSE]]
[1] 18 19

The phenomenon is called partial matching (see ?pmatch):

> pmatch("ag", names(village))
[1] 1