为矢量中的每个值指定一个负号（在R中）？

Question

I want this:

V <- c(2, 3, 4, 5, 6)
V <- as.data.frame(V)

To look like this:

[1] -2 -3 -4 -5 -6

Essentially the reverse of the abs() function. Thanks.

Answer 1

I believe that if you don't know beforehand whether all values of the vector are positive, then you should do something like the code below.

V <- c(2, 3, 4, 5, 6)
W <- c(-2, -3, -4, -5, -6)
X <- c(2, -3, 4, -5, 6)

all.neg <- function(x) -1*abs(x)

Let's try it.

all.neg(V)
#[1] -2 -3 -4 -5 -6

all.neg(W)
#[1] -2 -3 -4 -5 -6

all.neg(X)
#[1] -2 -3 -4 -5 -6

If you want to apply it to a data.frame, then do it the usual way.

dat <- data.frame(V, W, X)

dat[] <- lapply(dat, all.neg)
dat
#   V  W  X
#1 -2 -2 -2
#2 -3 -3 -3
#3 -4 -4 -4
#4 -5 -5 -5
#5 -6 -6 -6

Answer 2

You could do

 V * -1

or

-V # first mentioned in the comments by @RHertel

or anything like that. With assignment (updating the object) it looks like this:

v <- v * -1 # or -V

You can also use = for assignment but it goes against the style guides.

[1] -2 -3 -4 -5 -6