How to get row from R dataframe

Question

I have a dataframe with column headers.

How can I get a specific row from the dataframe as a list (with the column headers as keys for the list)?

Specifically, my dataframe is

    A B C
1   5 4.25 4.5
2   3.5 4 2.5
3   3.25 4 4
4   4.25 4.5 2.25
5   1.5 4.5 3

And I want to get a row that's the equivalent of

> c(a=5, b=4.25, c=4.5)
  a   b   c 
5.0 4.25 4.5

Answer 1

Try:

> d <- data.frame(a=1:3, b=4:6, c=7:9)

> d
  a b c
1 1 4 7
2 2 5 8
3 3 6 9

> d[1, ]
  a b c
1 1 4 7

> d[1, ]['a']
  a
1 1

Answer 2

x[r,]

where r is the row you're interested in. Try this, for example:

#Add your data
x<-structure(list(A = c(5, 3.5, 3.25, 4.25, 1.5), B = c(4.25, 4, 
4, 4.5, 4.5), C = c(4.5, 2.5, 4, 2.25, 3)), .Names = c("A", "B", 
"C"), class = "data.frame", row.names = c(NA, -5L))

#The vector your result should match
y<-c(A=5, B=4.25, C=4.5)

#Test that the items in the row match the vector you wanted
x[1,]==y

This page (from this useful site) has good information on indexing like this.

Answer 3

If you don't know the row number, but do know some values then you can use subset

x<-structure(list(A = c(5, 3.5, 3.25, 4.25, 1.5), B = c(4.25, 4, 
4, 4.5, 4.5), C = c(4.5, 2.5, 4, 2.25, 3)), .Names = c("A", "B", 
"C"), class = "data.frame", row.names = c(NA, -5L))
subset(x, A ==5 & b==4.25 && c==4.5)