[英]Subset and replace rows and columns in a data.table
I need to modify certain columns of specific rows of a data.table. 我需要修改data.table的特定行的某些列。 I keep getting an error, "unused argument (with=F)".
我不断收到错误,“未使用的参数(带= F)”。 Does anyone know how to quickly deal with this?
有谁知道如何快速处理这个? Below is an example using both data.frames and data.table.
下面是使用data.frames和data.table的示例。
Thanks. 谢谢。
test.df <- data.frame(a=rnorm(100, 0, 1), b=rnorm(100, 0, 1), c=rnorm(100,0,1))
test.dt <- as.data.table(test.df)
test.df[test.df$a<test.df$b,c(1,2)] <- 10* test.df[test.df$a<test.df$b,c(1,2)]
test.dt[test.dt$a<test.dt$b, c(1,2), with=F] <- 10* test.dt[,c(1,2),with=F][test.dt$a<test.dt$b, c(1,2), with=F]
First of all - you do not need to, and should not (as a matter of good programming) use the data.table
name inside [.data.table
. 首先 - 你不需要,也不应该(作为一个好的编程问题)在
[.data.table
使用data.table
名称。
Secondly, you should avoid using column numbers whenever you can - this is a source of future headache, and should instead aim to use column names. 其次,你应该尽可能避免使用列号 - 这是未来头痛的根源,而应该使用列名。
Finally, the way to change columns in data.table
's is to use the :=
operator to modify in-place (see ?':='
). 最后,更改
data.table
列的方法是使用:=
运算符进行就地修改(参见?':='
)。
Combining all of the above, this is what you should do: 结合以上所有,这是你应该做的:
test.dt[a < b, `:=`(a = 10 * a, b = 10 * b)]
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