[R] calculate difference of consecutive cells in vector
Christos Hatzis
christos at silicoinsights.com
Wed Mar 22 21:57:47 CET 2006
Try
my.data$output <- diff(my.data$var1)
-Christos
-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Max Kauer
Sent: Wednesday, March 22, 2006 3:36 PM
To: r-help at stat.math.ethz.ch
Subject: [R] calculate difference of consecutive cells in vector
Hi
in dataframe I want to subtract the "next" value in the list from the former
one to get this:
name var1 output
a 9 506
b 515 512
c 1027 453
so I subtract: table$var1[2]-table$var1[1] and write it into table$output[1]
etc..
I did this with:
for (i in 1:(length(table$var1)){
table$output[i] <- table$var1[i+1]-table$var1[i] }
it works but it get extremely slow for a large table.
I bet there is a better way to do this in R with "sapply" or something
similiar, but I couldn't figure out how.
I'd apprechiate any idea
Thanks!
Max
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