Issue

This Content is from Stack Overflow. Question asked by keenan

In R, I have a dataframe df1 that looks like

name	location
a	T1
b	T2
c	T1

location corresponds to the name of another dataframe. I am trying to create a function to update the contents of this dataframe (in this case either T1 or T2).

My approach so far is as follows t <- df1$location[df1$name == "a"] and then pass t as an argument, but I do not know how to make the function access the dataframe thats name matches the value stored in t.

Solution

Using match.

transform(dat, value=cont$value[match(location, cont$loc)])
#   location name value
# 1       T1    a     1
# 2       T1    c     1
# 3       T2    b     2

Or merge.

merge(dat, cont, by.x='location', by.y='loc')
#   location name value
# 1       T1    a     1
# 2       T1    c     1
# 3       T2    b     2

Data:

dat <- structure(list(name = c("a", "b", "c"), location = c("T1", "T2", 
"T1")), class = "data.frame", row.names = c(NA, -3L))

cont <- structure(list(loc = c("T1", "T2"), value = 1:2), class = "data.frame", row.names = c(NA, 
-2L))

This Question was asked in StackOverflow by keenan and Answered by jay.sf It is licensed under the terms of CC BY-SA 2.5. - CC BY-SA 3.0. - CC BY-SA 4.0.