[R] Change the color of the line inside of the function lines

[Arnaud Michel]

Hi

I have the following problem :
I have 3 vectors xx, yy, zz :
xx <-  c(5479,  6209,  6940,  7670,  8766,  9496, 10227, 11048, 11778, 
12509, 13239, 13970,
14700, 15340, 15948)
yy <- c( 267, 275, 281, 287, 296, 306, 316, 325, 334, 351, 365, 377, 
389, 419, 419)
zz <- c( 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6)
I would like a line wich join the points (xx, yy) with stair steps (as 
type = "s")
plot(xx, yy, type="n")
lines(xx, yy, type ="s")
but I want to change the color according to the value of zz (exemple : 
col = 1 if zz =3 ; col =2 if zz= 4 ;  col =3 if zz= 5 ;  col =4 if zz= 6)
Thank you for your help

-- 
Michel ARNAUD
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