Visual Glossary of Terms

# Datetime
my_datetime <- Sys.time()
my_datetime

## [1] "2025-09-19 13:07:30 EDT"

class(my_datetime)

## [1] "POSIXct" "POSIXt"

# Character
# Convert car row names into characters
car_names <- rownames(mtcars)
head(car_names)

## [1] "Mazda RX4"         "Mazda RX4 Wag"     "Datsun 710"       
## [4] "Hornet 4 Drive"    "Hornet Sportabout" "Valiant"

class(car_names)

## [1] "character"

# Numeric
# Select numeric column (e.g. mpg)
mpg_values <- mtcars$mpg
head(mpg_values)

## [1] 21.0 21.0 22.8 21.4 18.7 18.1

class(mpg_values)

## [1] "numeric"

# Boolean
# Is mpg is greater than 15?
mpg_high <- mtcars$mpg > 15
head(mpg_high)

## [1] TRUE TRUE TRUE TRUE TRUE TRUE

class(mpg_high)

## [1] "logical"

# Array
# Convert subset of mtcars to array
mtcars_array <- array(data = as.matrix(mtcars[1:6, 1:3]), dim = c(2, 3, 3))
mtcars_array

## , , 1
## 
##      [,1] [,2] [,3]
## [1,]   21 22.8 18.7
## [2,]   21 21.4 18.1
## 
## , , 2
## 
##      [,1] [,2] [,3]
## [1,]    6    4    8
## [2,]    6    6    6
## 
## , , 3
## 
##      [,1] [,2] [,3]
## [1,]  160  108  360
## [2,]  160  258  225

class(mtcars_array)

## [1] "array"

# Vector
# A single numeric vector from mtcars
hp_vector <- mtcars$hp
head(hp_vector)

## [1] 110 110  93 110 175 105

class(hp_vector)

## [1] "numeric"

#Dataframe (mtcars is already one)
mtcars_df <- mtcars[1:5, ]
mtcars_df

##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2

class(mtcars_df)

## [1] "data.frame"

# List 
# A list with different types from mtcars
mtcars_list <- list(
  name = rownames(mtcars)[1],
  mpg = mtcars$mpg[1],
  high_mpg = mtcars$mpg[1] > 20
)
mtcars_list

## $name
## [1] "Mazda RX4"
## 
## $mpg
## [1] 21
## 
## $high_mpg
## [1] TRUE

class(mtcars_list)

## [1] "list"

# Tibble
library(tibble)
mtcars_tibble <- as_tibble(mtcars)
head(mtcars_tibble)

## # A tibble: 6 × 11
##     mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
##   <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
## 1  21       6   160   110  3.9   2.62  16.5     0     1     4     4
## 2  21       6   160   110  3.9   2.88  17.0     0     1     4     4
## 3  22.8     4   108    93  3.85  2.32  18.6     1     1     4     1
## 4  21.4     6   258   110  3.08  3.22  19.4     1     0     3     1
## 5  18.7     8   360   175  3.15  3.44  17.0     0     0     3     2
## 6  18.1     6   225   105  2.76  3.46  20.2     1     0     3     1

class(mtcars_tibble)

## [1] "tbl_df"     "tbl"        "data.frame"