Importing a data-set from Excel

  • The read_excel() function from the readxl package (included in tidyverse) is used to import files created by Microsoft Excel.
  • Alternatively: R Studio provided an easy way to import data:
    File Import Dataset From Excel
  • But if you want to have a full script that runs by itself, I recommend to use the R functions.
  • Store your data within your R project folder.
  • If you do not install it there, you need to know the folder location to load it into R.

Example

library(readxl)
dat <- read_xlsx("res/cars.xlsx")
names(dat) # this function shows the variable names of a data frame 
 [1] "mpg"  "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear"
[11] "carb"
mpg cyl disp hp drat wt qsec vs am gear carb
21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2
18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1
14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4
24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4
17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4
16.4 8 275.8 180 3.07 4.070 17.40 0 0 3 3
17.3 8 275.8 180 3.07 3.730 17.60 0 0 3 3
15.2 8 275.8 180 3.07 3.780 18.00 0 0 3 3
10.4 8 472.0 205 2.93 5.250 17.98 0 0 3 4
10.4 8 460.0 215 3.00 5.424 17.82 0 0 3 4
14.7 8 440.0 230 3.23 5.345 17.42 0 0 3 4
32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
15.5 8 318.0 150 2.76 3.520 16.87 0 0 3 2
15.2 8 304.0 150 3.15 3.435 17.30 0 0 3 2
13.3 8 350.0 245 3.73 3.840 15.41 0 0 3 4
19.2 8 400.0 175 3.08 3.845 17.05 0 0 3 2
27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
15.8 8 351.0 264 4.22 3.170 14.50 0 1 5 4
19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6
15.0 8 301.0 335 3.54 3.570 14.60 0 1 5 8
21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2

Task

  • Download the Excel file “cars.xlsx” from the moodle course.
  • Save it in your project directory.
  • Import the data set and assign it to an object dat.
  • Apply the View() function to see the dataset.

Note: View() opens a new tab in RStudio with the content of a data frame (e.g. View(dat)).

Task

  • Calculate the mean of mpg (miles per gallon) for cars with 4, 6, and 8 cylinders (variable cly).

:-)

Task - solution

  • Calculate the mean of mpg (miles per gallon) for cars with 4, 6, and 8 cylinders (variable cly).
mean(dat$mpg[dat$cyl == 4])
mean(dat$mpg[dat$cyl == 6])
mean(dat$mpg[dat$cyl == 8])
[1] 26.66364
[1] 19.74286
[1] 15.1