On Jul 18, 2010, at 10:09 PM, Seth wrote:
Hi,
What I would like to do is have a data.frame with column names and
have
these column names stored as strings in another vector. Then I
would like
to be able to access the data.fram columns via referencing the
vector of
names. The code below shows the last few executions that failed to
retrieve
the values for column named X1. Seth
table.1<-cbind(c(1,2,3,2,2),c(0,9,0,7,9),c(7,5,9,8,8))
table.1
[,1] [,2] [,3]
[1,] 1 0 7
[2,] 2 9 5
[3,] 3 0 9
[4,] 2 7 8
[5,] 2 9 8
table.1<-data.frame(table.1)
table.1
X1 X2 X3
1 1 0 7
2 2 9 5
3 3 0 9
4 2 7 8
5 2 9 8
hold<-c("X1","X2","X3")
hold
[1] "X1" "X2" "X3"
table.1$X1
[1] 1 2 3 2 2
hold[1]
[1] "X1"
table.1$hold[1] # FROM HERE DOWN ARE MY ATTEMPTS TO ACCESS X1
NULL
Try instead:
table.1[ , hold[1] ]
The "$" formalism does not evaluate its argument, but the "[" function
does.
--
David.
table.1$(hold[1])
Error: unexpected '(' in "table.1$("
table.1$get(hold[1])
Error: attempt to apply non-function
table.1$(get(hold[1]))
Error: unexpected '(' in "table.1$("
--
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and provide commented, minimal, self-contained, reproducible code.
