Create date sequence by factor level

Question

I have a list of 100 observation units and a sequence of dates:

unit <- c(1:100)
date <- seq.Date(as.Date("2012-01-01"),as.Date("2012-12-01"), by = "month")

I want to create a new dataframe with each observational unit having a time unit. For example:

Unit     Date
 1    "2012-01-01"
 1    "2012-02-01"
 1    "2012-03-01"
 1    "2012-04-01"
 ................
 100   "2012-01-01"
 100   "2012-02-01"
 100   "2012-03-01"
 100   "2012-04-01"

Gopala · Accepted Answer · 2016-04-12 20:11:22Z

3

You can use the following:

expand.grid(unit = unit, date = date)

If this is what you have in mind.

You can optionally order by unit as follows:

df <- expand.grid(unit = unit, date = date)
df <- df[order(df$unit), ]

answered Apr 12, 2016 at 20:11

Gopala

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1 Comment

Gio Circo Over a year ago

A simple answer. Works great. Thanks!

JohnSG · Accepted Answer · 2016-04-12 20:14:49Z

3

Not as concise as expand.grid, but more explicitly, you could do:

examp <- data.frame(Unit = rep(unit, each = length(date)), 
                    Date = rep(date, times = length(unit)))

answered Apr 12, 2016 at 20:14

JohnSG

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