Bastien Bastien - 25 days ago 10
R Question

Challenging vector modification

I have what appears to be a simple problem but I can't figure out a way to fix it simply. I need to find a way to transform a numerical vector a way that it is increasing. A example will be clearer...

vec1 <- c(3,3,2,3,1)


After passe into a function


f(vec1)


should become

# [1] 1 1 2 1 3


The same way,

vec2 <- c(1,3,1,2,7)


should become

# [1] 1 2 1 3 4


and

vec3 <- c(2,1,0,0,4)


should become

# [1] 1 2 3 3 4


Initially I've though that

as.numeric(as.factor(vec1))


would have worked but it's not working anymore (new version?)

For people that wonder why I need that, it's related to a bug in the raster package which I've presented here:
http://r-sig-geo.2731867.n2.nabble.com/bug-in-raster-stackApply-when-raster-not-in-memory-td7590584.html

but got no answer. I then have to find a workaround.

I hope it's clear,
Thanks

Answer

We can create a function with match

f1 <- function(x){
     match(x, unique(x))
}

f1(vec1)
#[1] 1 1 2 1 3
f1(vec2)
#[1] 1 2 1 3 4