Find mean of all numeric columns of a Data Frame
lapply(mtcars, class) # find class of all predictors
## $mpg
## [1] "numeric"
##
## $cyl
## [1] "character"
##
## $disp
## [1] "numeric"
##
## $hp
## [1] "numeric"
##
## $drat
## [1] "numeric"
##
## $wt
## [1] "numeric"
##
## $qsec
## [1] "numeric"
##
## $vs
## [1] "numeric"
##
## $am
## [1] "character"
##
## $gear
## [1] "character"
##
## $carb
## [1] "numeric"
mtcars[, sapply(mtcars, is.numeric)]
## mpg disp hp drat wt qsec vs carb
## Mazda RX4 21.0 160.0 110 3.90 2.620 16.46 0 4
## Mazda RX4 Wag 21.0 160.0 110 3.90 2.875 17.02 0 4
## Datsun 710 22.8 108.0 93 3.85 2.320 18.61 1 1
## Hornet 4 Drive 21.4 258.0 110 3.08 3.215 19.44 1 1
## Hornet Sportabout 18.7 360.0 175 3.15 3.440 17.02 0 2
## Valiant 18.1 225.0 105 2.76 3.460 20.22 1 1
## Duster 360 14.3 360.0 245 3.21 3.570 15.84 0 4
## Merc 240D 24.4 146.7 62 3.69 3.190 20.00 1 2
## Merc 230 22.8 140.8 95 3.92 3.150 22.90 1 2
## Merc 280 19.2 167.6 123 3.92 3.440 18.30 1 4
## Merc 280C 17.8 167.6 123 3.92 3.440 18.90 1 4
## Merc 450SE 16.4 275.8 180 3.07 4.070 17.40 0 3
## Merc 450SL 17.3 275.8 180 3.07 3.730 17.60 0 3
## Merc 450SLC 15.2 275.8 180 3.07 3.780 18.00 0 3
## Cadillac Fleetwood 10.4 472.0 205 2.93 5.250 17.98 0 4
## Lincoln Continental 10.4 460.0 215 3.00 5.424 17.82 0 4
## Chrysler Imperial 14.7 440.0 230 3.23 5.345 17.42 0 4
## Fiat 128 32.4 78.7 66 4.08 2.200 19.47 1 1
## Honda Civic 30.4 75.7 52 4.93 1.615 18.52 1 2
## Toyota Corolla 33.9 71.1 65 4.22 1.835 19.90 1 1
## Toyota Corona 21.5 120.1 97 3.70 2.465 20.01 1 1
## Dodge Challenger 15.5 318.0 150 2.76 3.520 16.87 0 2
## AMC Javelin 15.2 304.0 150 3.15 3.435 17.30 0 2
## Camaro Z28 13.3 350.0 245 3.73 3.840 15.41 0 4
## Pontiac Firebird 19.2 400.0 175 3.08 3.845 17.05 0 2
## Fiat X1-9 27.3 79.0 66 4.08 1.935 18.90 1 1
## Porsche 914-2 26.0 120.3 91 4.43 2.140 16.70 0 2
## Lotus Europa 30.4 95.1 113 3.77 1.513 16.90 1 2
## Ford Pantera L 15.8 351.0 264 4.22 3.170 14.50 0 4
## Ferrari Dino 19.7 145.0 175 3.62 2.770 15.50 0 6
## Maserati Bora 15.0 301.0 335 3.54 3.570 14.60 0 8
## Volvo 142E 21.4 121.0 109 4.11 2.780 18.60 1 2
lapply(mtcars, mean) # returns a list
## $mpg
## [1] 20.09062
##
## $cyl
## [1] NA
##
## $disp
## [1] 230.7219
##
## $hp
## [1] 146.6875
##
## $drat
## [1] 3.596563
##
## $wt
## [1] 3.21725
##
## $qsec
## [1] 17.84875
##
## $vs
## [1] 0.4375
##
## $am
## [1] NA
##
## $gear
## [1] NA
##
## $carb
## [1] 2.8125
sapply(mtcars, mean) # user-friendly alternative that returns a vector
## mpg cyl disp hp drat wt
## 20.090625 NA 230.721875 146.687500 3.596563 3.217250
## qsec vs am gear carb
## 17.848750 0.437500 NA NA 2.812500