[R] data.frame: temporal complexity

[ikuzar]

Hello,

I created a data.frame which contains two columns: df$P (Power) et
df$DateTime (time). I'd like to add a new column df$diffP (difference of
Power between T and T-2).

I made a loop :

for (i in 3:length(df$DateTime)){
    df$diffP[i] = df$P[i] - df$P[i-2] 
}
execution time result is unaceptable: 24s !!

Is there any way to reduce complexity about O(n) ? for example 2 or 3s (10s
maxi)

Does anybody find better than ~24s ?

thanks for your help

--
View this message in context: http://r.789695.n4.nabble.com/data-frame-temporal-complexity-tp4269585p4269585.html
Sent from the R help mailing list archive at Nabble.com.