Hi Marlene,
x=data.frame(y,vr=NA)
for(i in 4:nrow(x)) x[i,"vr"] =var(y[(i-3):(i-1)])
will do the trick, solving both problems with overwriting subsequent
x-values and obeying the precedence of R operators.
For the latter, see ?Syntax and compare
i<-5
i-3:i-1
(i-3):(i-1)
hth.
marlene marchena schrieb:
Dear R-user
Suppose I have the following data
y=c(2,1,5,8,11,3,1,7,50,21,33,7,60)
x=data.frame(y)
for(i in 4:nrow(x)) x[i,] =var(x[i-3:i-1,])
I'm trying to get a new variable with the variance of the 3 previous values
(just an example) and with NA in the three first positions. I know that my
for() is wrong
but I'm not able to find my error.
Any idea?
Thanks,
Marlene.
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