[R] Confused about using data.table package,
tmrsg11 at gmail.com
Tue Feb 21 03:53:29 CET 2017
While I got your attention, what is a good way to get started on ggplot2? ;)
My impression is that I first need to learn plyr, dplyr, AND THEN ggplot2.
That's A LOT!
Suppose i have this:
iris2 <- cbind(iris, grade = sample(1:5, 150, replace = TRUE))
I want to have some kind of graph conditioned on species, by grade . What's
a good lead to learn about plotting this?
On Mon, Feb 20, 2017 at 11:12 AM, Hadley Wickham <h.wickham at gmail.com>
> On Sun, Feb 19, 2017 at 3:01 PM, David Winsemius <dwinsemius at comcast.net>
> >> On Feb 19, 2017, at 11:37 AM, C W <tmrsg11 at gmail.com> wrote:
> >> Hi R,
> >> I am a little confused by the data.table package.
> >> library(data.table)
> >> df <- data.frame(w=rnorm(20, -10, 1), x= rnorm(20, 0, 1), y=rnorm(20,
> 10, 1),
> >> z=rnorm(20, 20, 1))
> >> df <- data.table(df)
> > df <- setDT(df) is preferred.
> Don't you mean just
> setDT() modifies by reference.
> >> df_3 <- df[, a := x-y] # created new column a using x minus y, why are
> >> using colon equals?
> > You need to do more study of the extensive documentation. The behavior
> of the ":=" function is discussed in detail there.
> You can get to that documentation with ?":="
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