Message-ID: <CAE2FW2=QOrHTkGjy3xUin6NdMnq=z09PTSE_cGfcQVL5gf6sAQ@mail.gmail.com>
Date: 2017-02-19T19:37:13Z
From: C W
Subject: Confused about using data.table package,
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)
#drop column w
df_1 <- df[, w := NULL] # I thought you are supposed to do: df_1 <- df[, -w]
df_2 <- df[x<y] # aren't you supposed to do df_2 <- df[x<y]?
df_3 <- df[, a := x-y] # created new column a using x minus y, why are we
using colon equals?
I am a bit confused by this syntax.
Thanks!
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