Extremeness of a case is calculated by the difference between a case's value on the independent variable and the variable's mean value.
Arguments
- lmobject
Object generated with
lm- ind_var
Independent variable for which extremeness values should be calculated. Has to be entered as a character.
Value
A dataframe with
- all variables in the linear model,
- absolute extremeness (absolute value of difference between variable score and mean value of variable),
- extremeness (difference between variable score and mean value of variable), which can be useful when the direction of extremeness is relevant.
The rows are ordered in decreasing order of the absolute extreme values.
Details
Calculating the absolute value of the difference between the cases' values and the variable's mean value is proposed by Seawright, Jason (2016): The Case for Selecting Cases That Are Deviant or Extreme on the Independent Variable. Sociological Methods & Research 45 (3): 493-525. (doi:10.1177/0049124116643556 )
Examples
df <- lm(mpg ~ disp + wt, data = mtcars)
extreme_on_x(df, "wt")
#> mpg disp wt abs. extremeness extremeness
#> Lincoln Continental 10.4 460.0 5.424 2.20675 2.20675
#> Chrysler Imperial 14.7 440.0 5.345 2.12775 2.12775
#> Cadillac Fleetwood 10.4 472.0 5.250 2.03275 2.03275
#> Lotus Europa 30.4 95.1 1.513 1.70425 -1.70425
#> Honda Civic 30.4 75.7 1.615 1.60225 -1.60225
#> Toyota Corolla 33.9 71.1 1.835 1.38225 -1.38225
#> Fiat X1-9 27.3 79.0 1.935 1.28225 -1.28225
#> Porsche 914-2 26.0 120.3 2.140 1.07725 -1.07725
#> Fiat 128 32.4 78.7 2.200 1.01725 -1.01725
#> Datsun 710 22.8 108.0 2.320 0.89725 -0.89725
#> Merc 450SE 16.4 275.8 4.070 0.85275 0.85275
#> Toyota Corona 21.5 120.1 2.465 0.75225 -0.75225
#> Pontiac Firebird 19.2 400.0 3.845 0.62775 0.62775
#> Camaro Z28 13.3 350.0 3.840 0.62275 0.62275
#> Mazda RX4 21.0 160.0 2.620 0.59725 -0.59725
#> Merc 450SLC 15.2 275.8 3.780 0.56275 0.56275
#> Merc 450SL 17.3 275.8 3.730 0.51275 0.51275
#> Ferrari Dino 19.7 145.0 2.770 0.44725 -0.44725
#> Volvo 142E 21.4 121.0 2.780 0.43725 -0.43725
#> Duster 360 14.3 360.0 3.570 0.35275 0.35275
#> Maserati Bora 15.0 301.0 3.570 0.35275 0.35275
#> Mazda RX4 Wag 21.0 160.0 2.875 0.34225 -0.34225
#> Dodge Challenger 15.5 318.0 3.520 0.30275 0.30275
#> Valiant 18.1 225.0 3.460 0.24275 0.24275
#> Hornet Sportabout 18.7 360.0 3.440 0.22275 0.22275
#> Merc 280 19.2 167.6 3.440 0.22275 0.22275
#> Merc 280C 17.8 167.6 3.440 0.22275 0.22275
#> AMC Javelin 15.2 304.0 3.435 0.21775 0.21775
#> Merc 230 22.8 140.8 3.150 0.06725 -0.06725
#> Ford Pantera L 15.8 351.0 3.170 0.04725 -0.04725
#> Merc 240D 24.4 146.7 3.190 0.02725 -0.02725
#> Hornet 4 Drive 21.4 258.0 3.215 0.00225 -0.00225