Creating a column for year and quarter-CodePudding

I have a dataset, and the only variable that indicates time is t, being a series of numbers from 1-80, where when t=1 means Q1 1986, t=2 means Q2 1986, all the way to t=80 means Q4 2005.

I want to create another column that reads these periods as "Q1 1986" and "Q4 2005" etc.

CodePudding user response：

This can be done using modulos and integer division using some wrangling to avoid off-by-one errors because we start counting at 1.

paste0(
  "Q", (q - 1) %% 4   1, " ", 
  1986   (q - 1) %/% 4
)

CodePudding user response：

The yearqtr class in zoo can be used to represent year/quarter objects. Internally a yearqtr object is represented by the year fraction where fraction is 0 for Q1, 1/4 for Q2, 2/4 for Q3 and 3/4 for Q4. Note that if t=1 represents 1986 Q1 and numbers proceed sequentially by quarter then t=0, the origin, is 1985 Q4.

library(zoo)

# test input
DF <- data.frame(t = c(1, 80))

transform(DF, yq = format(as.yearqtr("1985-4")   t / 4, "Q%q %Y"))
##    t      yq
## 1  1 Q1 1986
## 2 80 Q4 2005

If the default output format, "%Y Q%q", is sufficient then it is even easier.

transform(DF, yq = as.yearqtr("1985-4")   t / 4)
##    t      yq
## 1  1 1986 Q1
## 2 80 2005 Q4