Sunday 2 September 2018

Statistical Functions - Graphics and Plots in R Language

Graphics tools :

Graphics tools - various type of plots
  • 2D & 3D plots,
  • scatter diagram
  • Pie diagram
  • Histogram
  • Bar plot
  • Stem and leaf plot
  • Box plot ....
Appropriate number and choice of plots in analysis provides better inferences.

In R, such graphics can be easily created and saved in various formats.
  • Bar plot
  • Pie chart
  • Box plot
  • Grouped box plot
  • Scatter plot
  • Coplots
  • Histogram
  • Normal QQ plot ...

Bar plots :-

→ Visualize the relative or absolute frequencies of observed values of a variable.
→ It consists of one bar for each category.
→ The height of each bar is determined by either the absolute frequency or the relative frequency of the respective category and is shown on the y-axis.

barplot (x, width = 1, space = NULL ,...)
> barplot (table (x) )
> barplot (table (x) / length (x) )

Example :-
Code the 10 persons by using, say 1 for male (M) and 2 for female (F).
  M, F, M, F, M, M, M, F, M, M
   1,  2, 1,  2,  1,  1,   1,  2,  1,  1

> gender <-  c(1, 2, 1, 2, 1, 1, 1, 2, 1, 1) 
> gender
 [1]  1  2  1  2  1  1  1  2  1  1



Example :-
> barplot (gender)
Do you want this ?
2 categories 
M = 7
F  = 3





Pie diagram :-

Pie charts visualize the absolute and relative frequencies.

A pie chart is a circle partitioned into segments where each of the segments represents a category.

The size of each segment depends upon the relative frequency and is determined by the angle (frequency x 360 degree).

pie (x,  labels  = names (x),  ...)

Example :-

> pie (gender)


Histogram :-

Histogram is based on the idea to categorize the data into different groups and plot the bars for each category with height.

The area of the bar (= height x width ) is proportional to the relative frequency.

So the width of the bars need not necessarily to be the same

hist (x)  # show absolute frequencies 
hist (x, freq=F)   # show relative frequencies

see help ("hist") for more details



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