There’s a time for generality, and there’s a time for solving the problem actually posed. This is one of the latter times. If you want to make a method that turns a sequence of doubles into a sequence of partial sums, then just do that: public static IEnumerable<double> CumulativeSum(this IEnumerable<double> sequence) { double sum = … Read more
You can call transform and pass the cumsum function to add that column to your df: In [156]: df[‘cumsum’] = df.groupby(‘id’)[‘val’].transform(pd.Series.cumsum) df Out[156]: id stuff val cumsum 0 A 12 1 1 1 B 23232 2 2 2 A 13 -3 -2 3 C 1234 1 1 4 D 3235 5 5 5 B 3236 … Read more
# replace the second column for the cumsum of the initial second column data[, 2] <- cumsum(data[, 2])
In analogy to the cumulative sum of a list I propose this: The cumulative average avg of a vector x would contain the averages from 1st position till position i. One method is just to compute the the mean for each position by summing over all previous values and dividing by their number. By rewriting … Read more
Here’s one way with ave: ave(df$a, cumsum(c(F, diff(df$a) < 0)), FUN=seq_along) – 1 [1] 0 1 2 3 0 1 2 3 4 5 6 0 1 0 We can get a running count grouped by diff(df$a) < 0. Which are the positions in the vector that are less than their predecessors. We add c(F, … Read more
UPDATE MySQL 8.0 introduces “window functions”, functionality equivalent to SQL Server “window functions” (with partitioning and ordering provided by Transact-SQL OVER syntax), and Oracle “analytic functions”. MySQL Reference Manual 12.21 Window Functions https://dev.mysql.com/doc/refman/8.0/en/window-functions.html The answer provided here is an approach for MySQL versions prior to 8.0. ORIGINAL ANSWER MySQL doesn’t provide the type analytic function … Read more
Basically, you need a window function. That’s a standard feature nowadays. In addition to genuine window functions, you can use any aggregate function as window function in Postgres by appending an OVER clause. The special difficulty here is to get partitions and sort order right: SELECT ea_month, id, amount, ea_year, circle_id , sum(amount) OVER (PARTITION … Read more
For those not using SQL Server 2012 or above, a cursor is likely the most efficient supported and guaranteed method outside of CLR. There are other approaches such as the “quirky update” which can be marginally faster but not guaranteed to work in the future, and of course set-based approaches with hyperbolic performance profiles as … Read more
MySQL 8.0/MariaDB supports windowed SUM(col) OVER(): SELECT *, SUM(cnt) OVER(ORDER BY id) AS cumulative_sum FROM tab; Output: ┌─────┬──────┬────────────────┐ │ id │ cnt │ cumulative_sum │ ├─────┼──────┼────────────────┤ │ 1 │ 100 │ 100 │ │ 2 │ 50 │ 150 │ │ 3 │ 10 │ 160 │ └─────┴──────┴────────────────┘ db<>fiddle