What's the opposite function to lag for an R vector/dataframe?

Question

I have a problem dealing with time series in R.

#--------------read data

wb = loadWorkbook(\"Countries_Europe_Prices.xlsx\") 
df = readWorksheet(wb, sheet=\"Sh         


        

Answer 1

There is an easier way of doing this which I have captured fully from this link. What I will do here is explaining what should you do in steps:

First create the following function by running the following code:

shift<-function(x,shift_by){
    stopifnot(is.numeric(shift_by))
    stopifnot(is.numeric(x))

    if (length(shift_by)>1)
        return(sapply(shift_by,shift, x=x))

    out<-NULL
    abs_shift_by=abs(shift_by)
    if (shift_by > 0 )
        out<-c(tail(x,-abs_shift_by),rep(NA,abs_shift_by))
    else if (shift_by < 0 )
        out<-c(rep(NA,abs_shift_by), head(x,-abs_shift_by))
    else
        out<-x
    out
}

This will create a function called shift with two arguments; one is the vector you need to operate its lag/lead and the other is number of lags/leads you need.

Example:

Suppose you have the following vector:

x<-seq(1:10)

x
 [1]  1  2  3  4  5  6  7  8  9 10

if you need x's first order lag

shift(x,-1)
[1] NA  1  2  3  4  5  6  7  8  9 

if you need x's first order lead (negative lag)

shift(x,1)
[1]  2  3  4  5  6  7  8  9 10 NA