Data Programming

Homework 1

Solutions

Submit a .html file created using Quarto via e-classroom. A sample is attached. Display all code (packages,input) and output.

Transform the dataframe automobile

automobile<-mtcars

1. Move rownames to a column cars.name, remove rownames.
2. Add a column named l/100km whose values are based on column mpg, then delete column mpg.
3. Change the am column to a factor with levels Automatic and Manual.

# solve 1-3 here
library(dplyr)
library(tibble)

# 1st task
automobile$cars.name <- rownames(automobile)
rownames(automobile) <- c(1:nrow(automobile))

# 2nd task
automobile$L100km <-  (235.214583 / automobile$mpg)
automobile <- automobile %>% select(-mpg)
      
# 3rd task
automobile$am <- automobile$am %>% factor(levels = c(0, 1), labels = c("Automatic", "Manual"))

After the transformation display the data frame as a tibble then answer these questions independently.

library(tidyverse)
as.tibble(automobile)

# A tibble: 32 × 12
     cyl  disp    hp  drat    wt  qsec    vs am      gear  carb cars.name L100km
   <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <fct>  <dbl> <dbl> <chr>      <dbl>
 1     6  160    110  3.9   2.62  16.5     0 Manual     4     4 Mazda RX4  11.2 
 2     6  160    110  3.9   2.88  17.0     0 Manual     4     4 Mazda RX…  11.2 
 3     4  108     93  3.85  2.32  18.6     1 Manual     4     1 Datsun 7…  10.3 
 4     6  258    110  3.08  3.22  19.4     1 Autom…     3     1 Hornet 4…  11.0 
 5     8  360    175  3.15  3.44  17.0     0 Autom…     3     2 Hornet S…  12.6 
 6     6  225    105  2.76  3.46  20.2     1 Autom…     3     1 Valiant    13.0 
 7     8  360    245  3.21  3.57  15.8     0 Autom…     3     4 Duster 3…  16.4 
 8     4  147.    62  3.69  3.19  20       1 Autom…     4     2 Merc 240D   9.64
 9     4  141.    95  3.92  3.15  22.9     1 Autom…     4     2 Merc 230   10.3 
10     6  168.   123  3.92  3.44  18.3     1 Autom…     4     4 Merc 280   12.3 
# ℹ 22 more rows

4. What is the average number of gears?
5. Return the rows with cars with horsepower between 200 and 400.
6. Which car is most fuel efficient car among 6 cylinder cars?

# solve 4-6 here
# 4
mean(automobile$gear) 

[1] 3.6875

# 5
automobile[c(automobile$hp>200 & automobile$hp<400),]

   cyl disp  hp drat    wt  qsec vs        am gear carb           cars.name
7    8  360 245 3.21 3.570 15.84  0 Automatic    3    4          Duster 360
15   8  472 205 2.93 5.250 17.98  0 Automatic    3    4  Cadillac Fleetwood
16   8  460 215 3.00 5.424 17.82  0 Automatic    3    4 Lincoln Continental
17   8  440 230 3.23 5.345 17.42  0 Automatic    3    4   Chrysler Imperial
24   8  350 245 3.73 3.840 15.41  0 Automatic    3    4          Camaro Z28
29   8  351 264 4.22 3.170 14.50  0    Manual    5    4      Ford Pantera L
31   8  301 335 3.54 3.570 14.60  0    Manual    5    8       Maserati Bora
     L100km
7  16.44857
15 22.61679
16 22.61679
17 16.00099
24 17.68531
29 14.88700
31 15.68097

# 6
(automobile %>% .[c(.$cyl == 6),] %>% .[order(.$"L100km", decreasing = F),])[1,]

  cyl disp  hp drat    wt  qsec vs        am gear carb      cars.name   L100km
4   6  258 110 3.08 3.215 19.44  1 Automatic    3    1 Hornet 4 Drive 10.99134