How to Group Days into Weeks

How can I group days into weeks?

Do you just want the number of completed 7 day intervals since the first record?

dvec <- as.Date("2001-04-01")+0:90
dweek <- as.numeric(dvec-dvec[1]) %/% 7
dweek[1:21]
# [1] 0 0 0 0 0 0 0 1 1 1 1 1 1 1 2 2 2 2 2 2 2

Group dates into weeks of the year, PHP

I don't think you need too much code to do it, You just need to find if the current post belongs to a specific week (number of the week in a year), then create a small logic to display additional markup based on that.

if ($posts) : ?>
    <div class="all-events events-container">
        <ul class="all-events-inner events-row">

            <?php
            // This will save the week that is being displayed
            $current_week = false;
            ?>
            <?php foreach ($posts as $post) : setup_postdata($post) ?>
                <?php
                // Get event start date
                $start_date = get_post_meta(get_the_ID(), 'event_date_time_start', true);
                // Find out this event week
                $week = date('WY', strtotime($start_date));

                // Check if this is the first time we are handling this week
                if ($week !== $current_week) {
                    // Store the current week so that we don't show the same output once again until next week
                    $current_week = $week;
                    // Get the first day of this week
                    $dateTime = new DateTime(date("Y-m-d", strtotime($start_date)));
                    $monday = $dateTime->modify('Monday this week');
                ?>
                    <li class="week-commencing">W/C <?php echo $monday->format('M d'); ?></li>
                <?php
                }
                ?>
                <li class="col-4 event">Blah blah stuff goes here</li>

            <?php endforeach; ?>

        </ul>
    </div>
<?php wp_reset_postdata();
endif;

Group dates by week in R

The code below calculates the current week relative to the minimum week in the data. week2 uses modular arithmetic to make the code more concise, although the week numbers don't always line up exactly with the direct calculation of years and week numbers using lubridate functions.

library(dplyr)
library(lubridate)

df2 %>% mutate(week = (year(Order_Date) - year(min(Order_Date)))*52 + 
                 week(Order_Date) - week(min(Order_Date)),
               week2 = (as.numeric(Order_Date) %/% 7) - (as.numeric(min(Order_Date)) %/% 7)) %>%
  arrange(Order_Date)

   Order_Date week week2
1  2015-10-23    0     0
2  2015-10-27    0     0
3  2015-11-01    1     1
4  2015-11-07    2     2
5  2015-11-11    2     2
6  2015-11-14    3     3
7  2015-12-17    8     8
8  2016-01-05   10    10
9  2016-01-20   12    12
10 2016-01-30   14    14
11 2016-02-18   16    17
12 2016-03-13   20    20
13 2016-03-31   22    23
14 2016-04-04   23    23
15 2016-04-15   25    25
16 2016-05-08   28    28
17 2016-05-10   28    28
18 2016-07-27   39    39
19 2016-10-01   49    49
20 2016-10-11   50    50

Group days into weeks with totals PySpark

Try with this approach using date_sub,next_day functions in spark.

Explanation:

date_sub(
        next_day(col("day"),"sunday"), //get next sunday date
   7)) //substract week from the date

Example:

In pyspark:

from pyspark.sql.functions import *
df = sc.parallelize([("2009-01-03","1","0"),("2009-01-09","14","0"),("2009-01-10","61","0")]).toDF(["day","bitcoin_total","dash_total"])
df.withColumn("week_strt_day",date_sub(next_day(col("day"),"sunday"),7)).groupBy("week_strt_day").agg(sum("bitcoin_total").cast("int").alias("bitcoin_total"),sum("dash_total").cast("int").alias("dash_total")).orderBy("week_strt_day").show()

Result:

+-------------+-------------+----------+
|week_strt_day|bitcoin_total|dash_total|
+-------------+-------------+----------+
|   2008-12-28|            1|         0|
|   2009-01-04|           75|         0|
+-------------+-------------+----------+

In scala:

import org.apache.spark.sql.functions._
val df=Seq(("2009-01-03","1","0"),("2009-01-09","14","0"),("2009-01-10","61","0")).toDF("day","bitcoin_total","dash_total") 
df.withColumn("week_strt_day",date_sub(next_day('day,"sunday"),7)).groupBy("week_strt_day").agg(sum("bitcoin_total").cast("int").alias("bitcoin_total"),sum("dash_total").cast("int").alias("dash_total")).orderBy("week_strt_day").show()