a <- c(1,2,3,4)
with condition a>2, I want to have a vector b = (0,0,1,1). currently I am using the following method. are there any simple methods?
b <- (a > 2)
b[b == TRUE] <- 1
b[b == FALSE] <- 0
There are a few ways you can go about this.
Using
ifelseb <- ifelse(a > 2, 1, 0)This is just a simpler way of writing exactly what you've written in the question: if the condition returns
TRUE, set the value to 1, otherwise set it to 0.Using
as.numericb <- as.numeric(a > 2)Logical values can be converted to their numeric equivalents easily using this function. As one might expect,
TRUEis set to 1 andFALSEto 0.The lazy version of
as.numericb <- 1*(a > 2)When R sees the multiplication of logical values by a numeric value, it automatically coerces the logicals to their numeric equivalents. Thus logical values can be converted lazily (from a programmer's standpoint) by multiplying by 1.
The way r codes logical data, your vector b <- a > 2 is already (0,0,1,1) - r stores "TRUE" values as 1's and "FALSE" values as 0's. You could even take mean(b) and it would return .5. If you'd prefer to visualize numbers instead of logical values however, you could always just do b <- as.numeric(b), or to put it all in one line of code b <- as.numeric(a > 2)
来源：https://stackoverflow.com/questions/30895845/r-vector-conditional-0-and-1