Six variations on ranking functions, mimicking the ranking functions
described in SQL2003. They are currently implemented using the built in
rank function, and are provided mainly as a convenience when
converting between R and SQL. All ranking functions map smallest inputs
to smallest outputs. Use desc() to reverse the direction.
Usage
row_number(x)
ntile(x = row_number(), n)
min_rank(x)
dense_rank(x)
percent_rank(x)
cume_dist(x)Arguments
- x
a vector of values to rank. Missing values are left as is. If you want to treat them as the smallest or largest values, replace with Inf or -Inf before ranking.
- n
number of groups to split up into.
Details
row_number(): equivalent torank(ties.method = "first")min_rank(): equivalent torank(ties.method = "min")dense_rank(): likemin_rank(), but with no gaps between rankspercent_rank(): a number between 0 and 1 computed by rescalingmin_rankto[0, 1]cume_dist(): a cumulative distribution function. Proportion of all values less than or equal to the current rank.ntile(): a rough rank, which breaks the input vector intonbuckets. The size of the buckets may differ by up to one, larger buckets have lower rank.
Examples
x <- c(5, 1, 3, 2, 2, NA)
row_number(x)
#> [1] 5 1 4 2 3 NA
min_rank(x)
#> [1] 5 1 4 2 2 NA
dense_rank(x)
#> [1] 4 1 3 2 2 NA
percent_rank(x)
#> [1] 1.00 0.00 0.75 0.25 0.25 NA
cume_dist(x)
#> [1] 1.0 0.2 0.8 0.6 0.6 NA
ntile(x, 2)
#> [1] 2 1 2 1 1 NA
ntile(1:8, 3)
#> [1] 1 1 1 2 2 2 3 3
# row_number can be used with single table verbs without specifying x
# (for data frames and databases that support windowing)
mutate(mtcars, row_number() == 1L)
#> mpg cyl disp hp drat wt qsec vs am gear carb
#> Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
#> Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
#> Datsun 710 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
#> Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
#> Hornet Sportabout 18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2
#> Valiant 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1
#> Duster 360 14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4
#> Merc 240D 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
#> Merc 230 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
#> Merc 280 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4
#> Merc 280C 17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4
#> Merc 450SE 16.4 8 275.8 180 3.07 4.070 17.40 0 0 3 3
#> Merc 450SL 17.3 8 275.8 180 3.07 3.730 17.60 0 0 3 3
#> Merc 450SLC 15.2 8 275.8 180 3.07 3.780 18.00 0 0 3 3
#> Cadillac Fleetwood 10.4 8 472.0 205 2.93 5.250 17.98 0 0 3 4
#> Lincoln Continental 10.4 8 460.0 215 3.00 5.424 17.82 0 0 3 4
#> Chrysler Imperial 14.7 8 440.0 230 3.23 5.345 17.42 0 0 3 4
#> Fiat 128 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
#> Honda Civic 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
#> Toyota Corolla 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
#> Toyota Corona 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
#> Dodge Challenger 15.5 8 318.0 150 2.76 3.520 16.87 0 0 3 2
#> AMC Javelin 15.2 8 304.0 150 3.15 3.435 17.30 0 0 3 2
#> Camaro Z28 13.3 8 350.0 245 3.73 3.840 15.41 0 0 3 4
#> Pontiac Firebird 19.2 8 400.0 175 3.08 3.845 17.05 0 0 3 2
#> Fiat X1-9 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
#> Porsche 914-2 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
#> Lotus Europa 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
#> Ford Pantera L 15.8 8 351.0 264 4.22 3.170 14.50 0 1 5 4
#> Ferrari Dino 19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6
#> Maserati Bora 15.0 8 301.0 335 3.54 3.570 14.60 0 1 5 8
#> Volvo 142E 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2
#> row_number() == 1L
#> Mazda RX4 TRUE
#> Mazda RX4 Wag FALSE
#> Datsun 710 FALSE
#> Hornet 4 Drive FALSE
#> Hornet Sportabout FALSE
#> Valiant FALSE
#> Duster 360 FALSE
#> Merc 240D FALSE
#> Merc 230 FALSE
#> Merc 280 FALSE
#> Merc 280C FALSE
#> Merc 450SE FALSE
#> Merc 450SL FALSE
#> Merc 450SLC FALSE
#> Cadillac Fleetwood FALSE
#> Lincoln Continental FALSE
#> Chrysler Imperial FALSE
#> Fiat 128 FALSE
#> Honda Civic FALSE
#> Toyota Corolla FALSE
#> Toyota Corona FALSE
#> Dodge Challenger FALSE
#> AMC Javelin FALSE
#> Camaro Z28 FALSE
#> Pontiac Firebird FALSE
#> Fiat X1-9 FALSE
#> Porsche 914-2 FALSE
#> Lotus Europa FALSE
#> Ford Pantera L FALSE
#> Ferrari Dino FALSE
#> Maserati Bora FALSE
#> Volvo 142E FALSE
mtcars %>% filter(between(row_number(), 1, 10))
#> mpg cyl disp hp drat wt qsec vs am gear carb
#> Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
#> Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
#> Datsun 710 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
#> Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
#> Hornet Sportabout 18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2
#> Valiant 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1
#> Duster 360 14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4
#> Merc 240D 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
#> Merc 230 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
#> Merc 280 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4