[R] programming to calculate variance

[Matthias Gondan]

I think it should be

var(y[i-3:i-1,])

instead of 

var(x[i-3:i-1,])

otherwise the values of the vector are overwritten

Best wishes,

Matthias



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.
>
> 	[[alternative HTML version deleted]]
>
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-- 
Dr. rer. nat. Matthias Gondan
Institut für Psychologie
Universität Regensburg
D-93050 Regensburg
Tel. 0941-943-3856
Fax 0941-943-3233
Email: matthias.gondan at psychologie.uni-regensburg.de
http://www.psychologie.uni-r.de/Greenlee/team/gondan/gondan.html