Changing date format from YY WW to DD-MM-YYYY

Question

I have a dataframe which look something like this

co_code   company_name   year   week   returns
1          A             2008    40     0.45
1          A             2008    41     0.33
1          A             2008    42     0.31
.
.
.
2          B             2002    01     0.22
2          B             2002    02     0.32
.
.
.

And so on. Years and week differs from company to company.

I want a separate column which replaces year and week into date. Here date should be last day of the week

Output should look something like this

co_code   company_name   date        returns
1          A             2008-10-11    0.45
1          A             2008-10-18    0.33
1          A             2008-10-25    0.31
.
.
.
2          B             2002-01-07    0.22
2          B             2002-01-14    0.32

Note:- This change should not affect ordering of dataframe. Rows should not get disturbed

Rushabh Patel · Accepted Answer · 2019-04-10T15:14:02.437

2

You can use this-

library(data.table)
setDT(dt)[,date:=as.Date(paste(year, week, 6, sep="-"), "%Y-%U-%u")]

Output-

co_code company_name year week returns       date
1:       1            A 2008   40    0.45 2008-10-11
2:       1            A 2008   41    0.33 2008-10-18
3:       1            A 2008   42    0.31 2008-10-25

Input data-

dt <- read.table(text="co_code   company_name   year   week   returns
1          A             2008    40     0.45
1          A             2008    41     0.33
1          A             2008    42     0.31",header=T)

Note- I have used 6th day of a week to match desired output. But, we can change that to whatever we required.

edited Apr 10 '19 at 15:14

answered Apr 10 '19 at 15:12

Rushabh Patel

2,672
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2

Why use 6 here?! – NelsonGon Apr 10 '19 at 15:13
to match his desired output – Rushabh Patel Apr 10 '19 at 15:14
we can change to what ever day of week we want. – Rushabh Patel Apr 10 '19 at 15:14
Agree but seems weird for a week to start on Saturday. Perhaps data specific. – NelsonGon Apr 10 '19 at 15:16
2

Yes. I agree. Indeed, I followed desired output. – Rushabh Patel Apr 10 '19 at 15:17
2

Also, I have added note for more clarification. – Rushabh Patel Apr 10 '19 at 15:17

Changing date format from YY WW to DD-MM-YYYY

1 Answers1