问题
I've imported the data from a text file and the negative numbers are in the form of 100- (The minus sign in the right side) and I should convert it into -100. Any idea. Thanks in advance.
回答1:
We can do this using sub. We capture the numbers as a group ((\\d+)) followed by a - at the end ($) of the string and replace with - followed by the backreference (\\1) of the capture group.
as.numeric(sub("([0-9.]+)-$", "-\\1", v1))
#[1] -100.50 -100.05 0.22 -22.00
data
v1 <- c(-100.5, '100.05-', 0.2200, '22.0-')
来源：https://stackoverflow.com/questions/41376835/how-to-move-minus-sign-from-right-to-left-back-to-front-in-r