Supporting Statistical Analysis for Research
5.3 Numeric variables
These exercises use the mtcars.csv data set.
Import the
mtcars.csvdata set.mtcars_path <- file.path("..", "datasets", "mtcars.csv") mtcars_in <- read_csv(mtcars_path, col_types = cols())Warning: Missing column names filled in: 'X1' [1]mtcars_in <- rename(mtcars_in, make_model = X1)mtcars <- mtcars_in glimpse(mtcars)Observations: 32 Variables: 12 $ make_model <chr> "Mazda RX4", "Mazda RX4 Wag", "Datsun 710", "Hornet... $ mpg <dbl> 21.0, 21.0, 22.8, 21.4, 18.7, 18.1, 14.3, 24.4, 22.... $ cyl <dbl> 6, 6, 4, 6, 8, 6, 8, 4, 4, 6, 6, 8, 8, 8, 8, 8, 8, ... $ disp <dbl> 160.0, 160.0, 108.0, 258.0, 360.0, 225.0, 360.0, 14... $ hp <dbl> 110, 110, 93, 110, 175, 105, 245, 62, 95, 123, 123,... $ drat <dbl> 3.90, 3.90, 3.85, 3.08, 3.15, 2.76, 3.21, 3.69, 3.9... $ wt <dbl> 2.620, 2.875, 2.320, 3.215, 3.440, 3.460, 3.570, 3.... $ qsec <dbl> 16.46, 17.02, 18.61, 19.44, 17.02, 20.22, 15.84, 20... $ vs <dbl> 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, ... $ am <dbl> 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ... $ gear <dbl> 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, ... $ carb <dbl> 4, 4, 1, 1, 2, 1, 4, 2, 2, 4, 4, 3, 3, 3, 4, 4, 4, ...The
wtvariable is measured in thousands of pounds. Change this variable to a character variable that has a comma separating the thousands digit from the hundreds digit, e.g. 2.14 becomes 2,140.Hint, for one of the possible solution you may find it useful to look for a tidyverse string function that will pad. Padding adds characters to a fixed width.
mtcars <- mtcars %>% mutate( wt_1000s = wt, wt = as.character(wt_1000s) ) %>% separate( wt, into = c("wt_d4", "wt_d123"), sep = "\\.", remove = TRUE ) %>% mutate( wt_d123 = str_pad(wt_d123, width = 3, side = "right", pad = "0") ) %>% unite(wt, wt_d4, wt_d123, sep = ",") mtcars %>% select(make_model, wt, wt_1000s) %>% head()# A tibble: 6 x 3 make_model wt wt_1000s <chr> <chr> <dbl> 1 Mazda RX4 2,620 2.62 2 Mazda RX4 Wag 2,875 2.88 3 Datsun 710 2,320 2.32 4 Hornet 4 Drive 3,215 3.22 5 Hornet Sportabout 3,440 3.44 6 Valiant 3,460 3.46This is another posible solution.
mtcars <- mtcars %>% mutate( wt = wt_1000s ) %>% select(-wt_1000s) mtcars <- mtcars %>% mutate( wt_1000s = wt, wt = as.character(wt * 1000), wt = str_replace(wt, "(...$)", ",\\1") ) mtcars %>% select(make_model, wt, wt_1000s) %>% head()# A tibble: 6 x 3 make_model wt wt_1000s <chr> <chr> <dbl> 1 Mazda RX4 2,620 2.62 2 Mazda RX4 Wag 2,875 2.88 3 Datsun 710 2,320 2.32 4 Hornet 4 Drive 3,215 3.22 5 Hornet Sportabout 3,440 3.44 6 Valiant 3,460 3.46Convert the character variable you created in the prior exercise to a new numeric variable. Make the units of measure for this new variable 1,000 of pounds.
mtcars <- mtcars %>% mutate( wt_1000s_new = parse_number(wt) / 1000 ) mtcars %>% select(make_model, wt, wt_1000s_new, wt_1000s) %>% head()# A tibble: 6 x 4 make_model wt wt_1000s_new wt_1000s <chr> <chr> <dbl> <dbl> 1 Mazda RX4 2,620 2.62 2.62 2 Mazda RX4 Wag 2,875 2.88 2.88 3 Datsun 710 2,320 2.32 2.32 4 Hornet 4 Drive 3,215 3.22 3.22 5 Hornet Sportabout 3,440 3.44 3.44 6 Valiant 3,460 3.46 3.46