Version: 10 November 2020
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help()
or short ?
function.install.packages()
function.After successful installation, add on packages have to be activated and loaded into memory in each R sesssion with the library()
function.
Note: You only install once, but you use library()
each time you restart R or R Studio.
Install the packages psych
and tidyverse
.
Activate both packages withlibrary(tidyverse)
library(psych)
install.packages(c("psych", "tidyverse"))
As soon as you have more tham one source file and/or external data, it makes sense to start a project
instead of just using single source
files.
The place on your harddrive R will save and load data from by default (i.e. when no other place is explicitly set). Use the getwd()
and setwd()
functions to get and set the working directory.
You can start a project
from R studio through:
read_excel()
function from the readxl
package (included in tidyverse
) is used to import files created by Microsoft Excel.library(readxl) dat <- read_xlsx("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 | 110 | 3.90 | 2.620 | 16.46 | 0 | 1 | 4 | 4 |
21.0 | 6 | 160 | 110 | 3.90 | 2.875 | 17.02 | 0 | 1 | 4 | 4 |
22.8 | 4 | 108 | 93 | 3.85 | 2.320 | 18.61 | 1 | 1 | 4 | 1 |
dat
.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)
).
mpg
(miles per gallon) for cars with 4, 6, and 8 cylinders (variable cly
).mpg
(miles per gallon) for cars with 4, 6, and 8 cylinders (variable cly
).dat_4 <- dat[dat[["cyl"]] == 4, "mpg"] dat_6 <- dat[dat[["cyl"]] == 6, "mpg"] dat_8 <- dat[dat[["cyl"]] == 8, "mpg"] mean(dat_4) mean(dat_6) mean(dat_8)
## [1] 26.66364
## [1] 19.74286
## [1] 15.1