Creating T-1 variable | R [duplicate]

Question

I would like to create a new variable sales.T.minus.1 which will present the value of sales from year - 1. I created a replicable example below:

  library(plm)
  library(dplyr)

  data <- pdata.frame(Cigar)
    
  data("Cigar")
    
  data <- data %>%
    mutate(sales.T.minus.1 = lag(sales, 1))

Unfortunately this code is not working. The value in variable sales.T.minus.1 is the same as in variable sales.

year	sales	sales.T.minus.1
64	95.4	95.4

How can I achieve the result I want?

The result I want is:

year	sales	sales.T.minus.1
64	95.4	93.9
65	98.5	95.4

Could you please explain what is not working? Do you get an error? — Quinten
– Quinten, Commented Mar 6, 2024 at 12:26
We can't really tell what result you get or what result you want from what you've presented. Please provide a reproducible example and the desired result. — DaveArmstrong
– DaveArmstrong, Commented Mar 6, 2024 at 12:26
Also, perhaps this answer will get you going in the right direction. — DaveArmstrong
– DaveArmstrong, Commented Mar 6, 2024 at 12:27
Try grouping by state. mutate(sales.T.minus.1 = lag(sales, 2), .by = state). Also, first load the data, then coerce to class 'pdata.frame'. (wrong instructions order in your code.) — Rui Barradas
– Rui Barradas, Commented Mar 6, 2024 at 12:35
@Quinten I edited my post, I think it is more reproducible :) — Viktor
– Viktor, Commented Mar 6, 2024 at 12:48

Quinten · Accepted Answer · 2024-03-06 12:51:52Z

2

Try using dplyr::lag because there may be some conflicting functions across package you have installed. And you want to use lag 1 instead of 2. When running it should work like this:

library(plm)
library(dplyr)

data("Cigar")

data <- pdata.frame(Cigar)

data <- data %>%
  mutate(sales.T.minus.1 = dplyr::lag(sales, 1))

^{Created on 2024-03-06 with reprex v2.0.2}

edited Mar 6, 2024 at 12:51

answered Mar 6, 2024 at 12:44

Quinten

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Comments

Murad Khalilov · Accepted Answer · 2024-03-06 12:53:03Z

0

if lag function doesnt work, then you can use shift function from data.table, it is faster than dplyr/lag


library(plm)
library(data.table)

data <- pdata.frame(Cigar)

data("Cigar")

data <- data %>%
  mutate(sales.T.minus.1 = data.table::shift(sales, n = 2, fill = NA))

answered Mar 6, 2024 at 12:53

Murad Khalilov

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