Simple R Functions

Loading the ‘mtcars’ dataset in R

## load mtcars dataset
data(mtcars)

PART 1 – Summarizing a Dataframe

Find total number of data points into mtcars dataset

# number of rows
nrow(mtcars)

## [1] 32

Find total number of columns into mtcars dataset

# number of columns
ncol(mtcars)

## [1] 11

Find total number of rows & columns into mtcars dataset

# number of rows & columns
dim(mtcars)

## [1] 32 11

Find the column names of the mtcars dataset

# column names
colnames(mtcars)

##  [1] "mpg"  "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear"
## [11] "carb"

Print the structure of the mtcars dataset

# structure of the data frame
str(mtcars)

## 'data.frame':    32 obs. of  11 variables:
##  $ mpg : num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
##  $ cyl : num  6 6 4 6 8 6 8 4 4 6 ...
##  $ disp: num  160 160 108 258 360 ...
##  $ hp  : num  110 110 93 110 175 105 245 62 95 123 ...
##  $ drat: num  3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
##  $ wt  : num  2.62 2.88 2.32 3.21 3.44 ...
##  $ qsec: num  16.5 17 18.6 19.4 17 ...
##  $ vs  : num  0 0 1 1 0 1 0 1 1 1 ...
##  $ am  : num  1 1 1 0 0 0 0 0 0 0 ...
##  $ gear: num  4 4 4 3 3 3 3 4 4 4 ...
##  $ carb: num  4 4 1 1 2 1 4 2 2 4 ...

PART 2 – Summarizing a Data Column within a Data Frame

Using $ to access columns within a dataframe

mtcars$mpg

##  [1] 21.0 21.0 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 17.8 16.4 17.3 15.2 10.4
## [16] 10.4 14.7 32.4 30.4 33.9 21.5 15.5 15.2 13.3 19.2 27.3 26.0 30.4 15.8 19.7
## [31] 15.0 21.4

Attach the dataframe

attach(mtcars)

Detach the dataframe

detach(mtcars)

Find the length of the variable ‘mpg’ in the mtcars data

# calculating the length
length(mtcars$mpg)

## [1] 32

Find the minimum of the variable ‘mpg’ in the mtcars data

# calculating the minimum value
min(mtcars$mpg)

## [1] 10.4

Find the maximum of the variable ‘mpg’ in the mtcars data

# calculating the maximum value
max(mtcars$mpg)

## [1] 33.9

Find the sum of the variable ‘mpg’ in the mtcars data

# calculating the sum
sum(mtcars$mpg)

## [1] 642.9

Find the mean of the variable ‘mpg’ in the mtcars data

# calculating the mean
mean(mtcars$mpg)

## [1] 20.09062