y <- sort(rnorm(20)) # say...
m <- s <- numeric(19)
for(i in 2:20) {
m[i-1] <- mean(y[1:i])
s[i-1] <- sd(y[1:i])
}
Easy peasy, ...
Bill Venables
CSIRO Laboratories
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-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of cvandy
Sent: Thursday, 31 January 2008 5:59 AM
To: r-help@r-project.org
Subject: [R] Loop with variable index
I have a list of 20 values. The first time through a loop I want to
find the
mean and stnd.dev. of the first two values; the second time through the
loop
I want to find the mean and stnd. dev. of the first 3 values, etc.
until
the last time through the loop I want to find the mean and stnd. dev. of
all
20 values, so I end up with 19 means and stnd. deviations.
How would I construct such a loop?
Thanks.
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and provide commented, minimal, self-contained, reproducible code.
