## Can we extract week numbers from the date

I got a dataframe df. Is there a way to populate the week numbers (as shown the second column in the dataframe). I mean the week numbers should be continuous. For example.

df <- structure(list(Date = structure(c(1527120000, 1527206400, 1527292800, 1527379200, 1527465600, 1527552000, 1527638400, 1527724800, 1527811200, 1527897600, 1527984000, 1528070400, 1528156800, 1528243200, 1528329600, 1528416000, 1528502400, 1528588800, 1528675200, 1528761600, 1528848000, 1528934400, 1529020800, 1529107200, 1529193600, 1529280000, 1529366400, 1529452800, 1529539200, 1529625600, 1529712000, 1529798400, 1529884800, 1529971200, 1530057600, 1530144000), class = c("POSIXct", "POSIXt" ), tzone = "UTC"), Week = c(1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 6)), row.names = c(NA, -36L), class = c("tbl_df", "tbl", "data.frame"))

Here the first date is `24-05-2018`

and hence it should be numbered as 1. The number should be continued for the next 6 days and then 2 should start for the next 7 days. After 4 week, the number should not be again 1, the number should be numbered as 5 and so on. So basically I need to check the mean of the list of time series for the span of 4 years. So right from day 1(say in 2000) to last day (say in 2014), the week number should be populated. Is there a way?

We can use `gl`

library(dplyr) df %>% mutate(Week = as.integer(gl(n(), 7, n())))

**Excel WEEKNUM function – convert week number to date and vice ,** To calculate the date range by the specific week number, you can use the following formulas: 1. Select a blank cell you will return the start date (in our case we In Microsoft Excel, you can extract a day of week from a date by using the WEEKDAY function. And you can use the following generic formula to get Monday immediately before any given date: = date - WEEKDAY (date - 2)

Date values are basically the number of seconds since a particular date. Here we can calculate the week offset with a bit of modulo math

df %>% mutate(NewWeek = as.numeric(Date-min(Date)) %/% (60*60*24*7) + 1)

We subtract off the first date, then see how many seven day periods have passed.

**How to convert week number to date or vice versa in Excel?,** To get the week number from the day from a date, you can use the WEEKNUM function. In the example shown, the formula in C5, copied down, To calculate the date range by the specific week number, you can use the following formulas: 1 . Select a blank cell you will return the start date (in our case we select the Cell B5), enter the formula: =MAX(DATE(B1,1,1),DATE(B1,1,1)-WEEKDAY(DATE(B1,1,1),2)+(B2-1)*7+1) , and press the Enter key.

You can use `lubridate`

:

library(lubridate) df$Data <- trunc((ymd(df$Date) - min(ymd(df$Date)))/dweeks(1)) + 1

`1`

is needed to start numbering of weeks from 1. `trunc`

gets rid of decimal places.

**Excel formula: Get week number from date,** To get the week number from the day from a date, you can use the WEEKNUM function. In the example shown, the formula in C5, copied down, is: =WEEKNUM(B5) If you want to get the week number with the year, Grant Shannon's solution using strftime works, but you need to make some corrections for the dates around january 1st. For instance, 2016-01-03 (yyyy-mm-dd) is week 53 of year 2015, not 2016. And 2018-12-31 is week 1 of 2019, not of 2018. This codes provides some examples and a solution.

You can also try:

df %>% mutate(Week = ceiling(row_number()/7)) Date Week <dttm> <dbl> 1 2018-05-24 00:00:00 1 2 2018-05-25 00:00:00 1 3 2018-05-26 00:00:00 1 4 2018-05-27 00:00:00 1 5 2018-05-28 00:00:00 1 6 2018-05-29 00:00:00 1 7 2018-05-30 00:00:00 1 8 2018-05-31 00:00:00 2 9 2018-06-01 00:00:00 2 10 2018-06-02 00:00:00 2

It does not take into account the dates, it just groups together every 7 rows.

The same with `base R`

:

ceiling(1:NROW(df)/7) [1] 1 1 1 1 1 1 1 2 2 2 2 2 2 2 3 3 3 3 3 3 3 4 4 4 4 4 4 4 5 5 5 5 5 5 5 6

**How to use the Excel WEEKNUM function,** This post will guide you how to convert a week number to a date with a formula in Excel. How do I calculate a date from a week number and a You need to create a formula based on the MAX function, the DATE function and the WEEKDAY function to convert week number to a date in Excel. Just do the following steps: #1 Type the year number in Cell C1, and type the week number in Cell C2. #2 Type this formula into the formula box of the Cell C3, then press Enter key in your keyboard. The Serial number of the start date is calculated in Cell C3.

**Converting Week Number to Date - Free Excel Tutorial,** Actually, I think you may have discovered a bug in the week() function, or at least an error in the documentation. Hopefully someone will jump in and explain why The EXTRACT function extracts a portion of a dateTime value, such as the day of the week or month of the year. This can be useful in situations where the data must be filtered or grouped by a slice of its timestamps, for example to compute the total sales that occurred on any Monday.

**How to get week numbers from dates?,** Calculate the week number of any date and find the beginning and end date of a specific week Birthday Calculator – Find when you are 1 billion seconds old To get the week number from the day from a date, you can use the WEEKNUM function. In the example shown, the formula in C5, copied down, is: =WEEKNUM(B5) With the date January 5, 2016 in B5, WEEKNUM returns 2 as the

**Week Number Calculator: What Week of the Year Is It?,** So, I wanted to share some of the formulas and calculations I used to calculate week numbers. These tips will also be useful for financial Replace Time.now with Time.local(year,month,day) for other dates. Formats: %U - Week number of the year, starting with the first Sunday as the first day of the first week (00..53) %V - Week number of year according to ISO-8601 (01..53) %W - Week number of the year, starting with the first Monday as the first day of the first week (00..53) Go