Lab 4: Visualization

Bar Plot - usually used for quaLitative variable - to make comparison.

barplot( frequency-table , 
          main = "title" , 
          ylab = "y-axis-label",
          xlab = "x-axis-label",
          col = "" ,
          border = " " ,
          space = #space-btween-bars ,
          ylim = c( start# , stop# ))

gender - f , f, m, f, m, f, m, f, f, m,

gender <- c("f", "f","m", "f", "m", "f", "m", "f", "f","m" )

# frequency table
table(gender)

## gender
## f m 
## 6 4

# barplot
barplot( table(gender) ,
         main = "Bar plot for Gender",
         xlab = "Gender",
         ylab = "Frequency",
         space = 1.5,
         ylim = c(0, 8),
         col = "skyblue",
         border = "darkblue")

Built in Dataset

R has built in data-sets.
To display a list of data-sets, we run data() within the CONSOLE.
To call a specific data set, call its exact name in the list.
To see the background story of the data set, we run help( data-set-name ) within the CONSOLE.

# show the first 5 rows of the data set
head(ChickWeight, n=5)

##   weight Time Chick Diet
## 1     42    0     1    1
## 2     51    2     1    1
## 3     59    4     1    1
## 4     64    6     1    1
## 5     76    8     1    1

# show the last 5 rows of the data set
tail(ChickWeight, n=5)

##     weight Time Chick Diet
## 574    175   14    50    4
## 575    205   16    50    4
## 576    234   18    50    4
## 577    264   20    50    4
## 578    264   21    50    4

# check structure
str(ChickWeight)

## Classes 'nfnGroupedData', 'nfGroupedData', 'groupedData' and 'data.frame':   578 obs. of  4 variables:
##  $ weight: num  42 51 59 64 76 93 106 125 149 171 ...
##  $ Time  : num  0 2 4 6 8 10 12 14 16 18 ...
##  $ Chick : Ord.factor w/ 50 levels "18"<"16"<"15"<..: 15 15 15 15 15 15 15 15 15 15 ...
##  $ Diet  : Factor w/ 4 levels "1","2","3","4": 1 1 1 1 1 1 1 1 1 1 ...
##  - attr(*, "formula")=Class 'formula'  language weight ~ Time | Chick
##   .. ..- attr(*, ".Environment")=<environment: R_EmptyEnv> 
##  - attr(*, "outer")=Class 'formula'  language ~Diet
##   .. ..- attr(*, ".Environment")=<environment: R_EmptyEnv> 
##  - attr(*, "labels")=List of 2
##   ..$ x: chr "Time"
##   ..$ y: chr "Body weight"
##  - attr(*, "units")=List of 2
##   ..$ x: chr "(days)"
##   ..$ y: chr "(gm)"

# check dimension: row x column
dim(ChickWeight)

## [1] 578   4

# check for column names
colnames(ChickWeight)

## [1] "weight" "Time"   "Chick"  "Diet"

# generate bargraph for column Diet in ChickWeight
# access column: data-set-name$column-name
barplot( table(ChickWeight$Diet),
         main = "Bar plot of different diet for chicken",
         ylab = "Counts",
         xlab = "Diet Types",
         space = 1.25, 
         ylim = c(0,250),
         col = "#4361ee",
         border = "#dc2f02")

Histogram - usually used for numeric variable - to show the spread/variability of the distribution.

hist( variable ,
      main = "" ,
      xlab = "",
      ylab = "" ,
      col = " " ,
      border = " " ,
      xlim = c( start# , stop#) ,
      ylim = c( start# , stop#) )

exam - 9, 10, 7, 6, 8, 4, 5, 9, 10, 8, 7, 7, 6, 6, 8, 10, 9, 10, 9, 10, 10

exam <- c(9, 10, 7, 6, 8, 4, 5, 9, 10, 8, 7, 7, 6, 6, 8, 10, 9, 10, 9, 10, 10)

# generate histogram
hist(exam, 
     main = "Histogram of Exam Scores",
     xlab = "Scores",
     xlim = c(0, 12),
     ylim = c(0,7),
     col = "#52b788")

Histogram with a data-set.

colnames(ChickWeight)

## [1] "weight" "Time"   "Chick"  "Diet"

hist( ChickWeight$weight,
      main = "Histogram of Chicken Weight",
      xlab = "Weight (gm)",
      ylim = c(0,250),
      col = "#9381ff")

Boxplot - usually used for numeric variable - to show the spread and quartile of the set of the score.

boxplot ( variable ,
          main = " " ,
          ylab = " " ,
          col = " " , 
          border = " " ,
          horizontal = TRUE-or-FALSE)