R数据。表创建一个带有条件的变量。

I need to create a new variable in the dataset below:

我需要在数据集中创建一个新的变量:

A  X
a  1
b  2
c  3
d  4
e  5
f  6
g  7
h  8
i  9
j 10

The newvar will have value 1 if X equals 2,5,7 or 9. Otherwise, newvar should be 0.

如果X等于2、5、7或9，则新var的值为1。否则，newvar应该是0。

Code:

代码:

dt1 <- data.table(A = letters[1:10], X = 1:10, key = "X")
numberlist <- list(2,5,7,9)

I have tried the following based on a post here:

根据这里的一个帖子，我尝试了以下方法:

dt1[, newvar:=.SD, .SDcols = 0][%in% numberlist, newvar:=.SD, .SDcols = 1]
dt1[, newvar:=.SD, .SDcols = 0][X %in% numberlist, newvar:=.SD, .SDcols = 1]

dt1[, newvar:=.SD, .SDcols = 0] means "assign value of 0 to newvar as default option. The second bracket [%in% numberlist, newvar:=.SD, .SDcols = 1] means "if the key (X) is included in the numberlist, set the newvar value to 1.

dt₁[newvar:=。SD， . sdcols = 0]表示“将0赋给newvar为默认选项”。第二个括号[%在% numberlist中，newvar:=]。SD， . sdcols = 1]表示“如果数字列表中包含键(X)，则将newvar值设置为1”。

Any idea why it is not working?

你知道它为什么不工作吗?

1 个解决方案

#1

Try

试一试

dt1[, newvar:=(X %in% c(2,5,7,9))+0L][]
#     A  X newvar
# 1: a  1      0
# 2: b  2      1
# 3: c  3      0
# 4: d  4      0
# 5: e  5      1
# 6: f  6      0
# 7: g  7      1
# 8: h  8      0
# 9: i  9      1
#10: j 10      0

Or if we already have the matching elements stored in a a vector

或者如果我们已经将匹配元素存储在向量中

numberlist <- c(2,5,7,9)
dt1[, newvar:=as.numeric(X %in% numberlist)] 

as.numeric is another option to coerce the logical vector to 0/1 values.

作为。数字是将逻辑向量强制为0/1值的另一个选项。