On Tue, Jul 26, 2011 at 10:12 AM, Ista Zahn <iz...@psych.rochester.edu>
wrote:
> OK, easy enough:
>
> dat.tmp <- data.frame(id, month, value)
> my.plot <- function(dat) {print(dat[, c("id", "value")])}
> by(dat.tmp, id, my.plot)
Excellent. The output of that last line is:
* id value
1 1 10
2 1 12
3 1 11
4 1 14
5 1 16
id value
6 2 12
7 2 10
8 2 8
id value
9 3 14
10 3 11
11 3 15
id: 1
id value
1 1 10
2 1 12
3 1 11
4 1 14
5 1 16
------------------------------------------------------------
id: 2
id value
6 2 12
7 2 10
8 2 8
------------------------------------------------------------
id: 3
id value
9 3 14
10 3 11
11 3 15*
I want the second part (separated by IDs), and not the first part. I tried
this:
> by(dat.tmp, id, my.plot) -> output
Output has exactly what I want. However, the first part is still printed on
the screen. How can I prohibit the first part to be printed?
> Why? What do you have against loops?
Nothing personal! I just see this notion of avoiding loops and using R-style
functions over and over in my readings and my first R instructor also
mentioned R is a very powerful language as long as we avoid loops. I don't
have a thorough knowledge of why loops are not as efficient as vector-based
solutions, but I trust what I've heard and read.
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