difference between 2 ecdfs

Thanks to David and Zaihra for their help.

Besides plotting the difference between 2 ecdfs, I also would like it to
*look like* a step function. Any suggestion?

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of David Winsemius
Sent: Friday, March 21, 2008 8:51 PM
To: r-help at stat.math.ethz.ch
Subject: Re: [R] difference between 2 ecdfs

In article
<0FF736F1E306A446A88FD41FDDDC10AF1C77B0 at BWPW05.f2.enterprise>,

hi,
 
a) i have something like:
 
ecdfgrp1<-ecdf(subset(mydata,TMT_GRP==1)$Y);

ecdfgrp2<-ecdf(subset(mydata,TMT_GRP==2)$Y);

how can i plot the difference between these 2 step functions?
 
i could begin with ecdfrefl<-function(x){ecdfgrp2(x)-ecdfgrp1(x);} ...
what next?
 

#not tested  ...mydata not provided

ecrange<-range(mydata$Y)

plot(ecdfrefl(seq(from=ecrange[1],to=ecrange[2],by=0.2))

b) if i have a vector with repeated numeric values how can i get the 
subset without repeated values .e.g (0,4,0,2,2) ----> (0,4,2) ?
 

?unique

ttt<-c(1,3,5,5,5,7)
unique(ttt)

[1] 1 3 5 7

--
David Winsemius

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