This function makes it possible to control the ordering of window functions in R that don't have a specific ordering parameter. When translated to SQL it will modify the order clause of the OVER function.
Arguments
- order_by
a vector to order_by
- call
a function call to a window function, where the first argument is the vector being operated on
Details
This function works by changing the call to instead call
with_order() with the appropriate arguments.
Examples
order_by(10:1, cumsum(1:10))
#> [1] 55 54 52 49 45 40 34 27 19 10
x <- 10:1
y <- 1:10
order_by(x, cumsum(y))
#> [1] 55 54 52 49 45 40 34 27 19 10
df <- data.frame(year = 2000:2005, value = (0:5) ^ 2)
scrambled <- df[sample(nrow(df)), ]
wrong <- mutate(scrambled, running = cumsum(value))
arrange(wrong, year)
#> year value running
#> 1 2000 0 35
#> 2 2001 1 10
#> 3 2002 4 55
#> 4 2003 9 9
#> 5 2004 16 51
#> 6 2005 25 35
right <- mutate(scrambled, running = order_by(year, cumsum(value)))
arrange(right, year)
#> year value running
#> 1 2000 0 0
#> 2 2001 1 1
#> 3 2002 4 5
#> 4 2003 9 14
#> 5 2004 16 30
#> 6 2005 25 55