CODEWITHSUNDEEP
r
David S
David S

Reputation: 193

Function for lagged sums

I know how to take the lagged difference:

delX = diff(x)

But the only way I know to take the lagged sum is:

sumY = apply(embed(c(0,y),2),1, sum)

Is there a function that can take the lagged sum? This way (or sliding the index in some other fashion) is not very intuitive.

Upvotes: 0

Views: 1086

Answers (2)

talat
talat

Reputation: 70266

Two more options:

x <- 1:10
x + dplyr::lag(x)
# [1] NA  3  5  7  9 11 13 15 17 19
x + data.table::shift(x)
# [1] NA  3  5  7  9 11 13 15 17 19

Note that you can easily change the number of lags in both functions. Instead of lagging, you can also create a leading vector by using dplyr::lead() or data.table::shift(x, 1L, type = "lead"). Both functions also allow you to specify default values (which are NA by default).

Upvotes: 0

Matthew Plourde
Matthew Plourde

Reputation: 44614

You're looking for filter:

x <- 1:10
filter(x, filter=c(1,1), sides=1)
# [1] NA  3  5  7  9 11 13 15 17 19

You could also use head and tail:

head(x, -1) + tail(x, -1)
# [1]  3  5  7  9 11 13 15 17 19

Upvotes: 3

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