Chapter-5:- Scatter Plot in R-programming

 Chapter-5:- Scatter Plot in R-programming

Example-1:- 

Create a scatter plot of car weight on x-axis and miles per gallon on y-axis by pre-program data "mtcars" in R-language

Code:-

mtcars

plot(mtcars$wt, mtcars$mpg,

     main = "Car Weight vs Fuel Efficiency",

     xlab = "car weight",

     ylab = "Miles Per Gallon",

     pch = 19,         # Solid circle shape

     col = "blue", # Change point color

     frame = FALSE)    # Remove the surrounding box

Result:-

Explanation:-

• In 1st line, "mtcars" is inbuilt program or database in R-programming language, you can in result image with yellow square box, it contain multiple car model with mpg, disp, wt, gear, carb etc. 
• In 2nd line plot() use, we discuss this already in previous chapter it contain multiple parameter like col, lwd, lty, col, xlim, ylim etc.
• In 2nd line, you see mtcars$wt, here you see $ sign, it use mainly to collect data from specific column like here we use wt, so it collect data of wt column of different model of cars
• Also we use mtcars$mpg, it means it collect data from mpg column of database
• In last line, frame if TRUE it make a box around it, if FALSE then you see no box surround the result image

Example-2:-

Plot sepal length vs sepal width for all species, set the x-axis range from 4 to 8 and y-axis from 2 to 4.5 by pre-program database "iris"

Code:-

iris

plot(iris$Sepal.Length, iris$Sepal.Width,

     col = c("blue", "yellow"),    # For color of the sepal

     pch = 19,                    # solid circle denote by 19

     main = "Custom Species Colors")   #main title

Result:-

Explanation:-

• Iris is also pre-program or inbuilt data base in R-programming language like the "mtcars"
• You can see in result image in yellow square box, "iris" contain 5 different column like Sepal.length, Sepal.width, species etc.
• If you want to collect data from specific column like Sepal.Length then we use $ sign as you can see in 2nd line code
• For use different color, use c(1st color name, 2nd color name), here c is compulsary to use, If you read previous chapter then no difficulty to understand
• pch- use for different shape/ symbol to denote
• main- for main title 

Example-3:- 

If in above example if ask to arrange the data according to petal width (means according to petal width the plot size increase or decrease, higher the petal width more size of plot in result graph)

Code:-

iris

plot(iris$Petal.Width,

     col = "red",    # For color of the sepal

     pch = 19,                    # solid circle denote by 19

     main = "Custom Species Colors",   #main title

     cex=iris$Petal.Width,    #Increase solid circle size according to value

     las=1,     # To make y-axis text horizontal

     frame.plot=FALSE)   #Remove top and right border of box

Result:-

Explanation:-

• Compare to previous example here additional command "cex" , frame.plot
• All the point already explain with comment in code

Example-4:-

Create a scatter plot of girth vs volume. Before plotting the points, add a light grey background grid using panel.first= grid() by using pre-program feature "trees", also add regression line to show the trend

Code:-

trees   #Load the database

plot(trees$Girth, trees$Volume,

     panel.first= grid(col="grey",lty="dotted"), #Create grid with background grey and dotted

     col="red",pch=20,cex=1.5)

#Add a red regression line

abline(lm(Volume ~ Girth, data = trees), col = "blue", lwd = 2)

Result:-

Explanation:-

• "trees" also inbuilt database in R-programming

Component	Function	Details
abline()	Draws a line	Function that draws a straight line on the plot
lm()	Fits a linear model	Calculate the best fit straight line that minimize the distance between line and your data points
Volume ~ Girth	Model formula	Means volume vs girth graph (use here “~”)
data	Specifies data	Like in this case trees which is inbuilt data
col	Color	Set the color of line
lwd	Line width	Sets the line width which default is 1

Example-5:-

Code:-

Result:-

Explanation:- 

1. The Global Mapping (aes)

The aes() (aesthetics) function maps your data variables to visual properties.

x,y	Horizontal and vertical position
color	Outline color of points, lines or borders
fill	Interior color for shapes
size	Diameter of points or thickness of lines
shape	Style of a point (0-25)
alpha	Transparency level (0 for transparent, 1 for opaque)
linetype	Pattern of a line (eg. solid, dashed, dotted)
group	Used to identify distinct sets of data

2. Geometric Layers (geom_*)

These parameters are often used outside of aes() to set "static" values for every point or line in that layer

data	Overrides the global dataset
stat	Overrides the default statistical transformation (eg stat= identity)
position	Adjusts how elements sit (eg. position= “dodge” for side-by-side bars)
na.rm	If TRUE, missing values are removed silently

3. Theme Customization (theme)

The theme() function controls non-data elements. It has nearly 100 parameters, categorized by "element functions" 

Text Element (element_text)	plot.title, axis.title.x, legend.text Parameters include family, face, size, hjust and vjust
Line Element (element_line)	panel.grid.major, axis.ticks Parameters include color, linewidth and linetype
Rectangle Elements (element_rect)	panel.background, plot.background Parameters include fill and color
Blank Elements (element_blank)	Removes an element entirely (eg. panel.grid.minor= element_blank()

4. Scales and Labels (scale_* & labs)

Scales translate data into the visual aesthetics you see

name	Axis or legend title
limits	Min/Max values of the scale
breaks	The specific points where labels/tick appear
labels	The text that appears at those breaks
labs()	A shortcut function to set title, subtitle, caption, x and y labels

5. Faceting and Coordinates (facet_* & coord_*)

Faceting	facet_wrap (~variable) facet_grid (rows~cols) Parameters include scales (eg. free_x) and nrow/ncol
Coordinates	coord_flip()       [swaps X and Y) coord_polar()    [circular plot) coord_cartesian ()      [zooming without removing data]

Chapter-4:- Line graph in R-programming

Example-1:-

Create a line graph showing a 5-day temperature trend using the vector temps <- c(22,24,23,26,25)

Requirements:-

Set the line type to solid with points at each data value

Color the line red and make it twice the default thickness

Add a title "Weekly Temperature" and label the axes "Day" and "Temp (C)

Code:-

temps <- c(22, 24, 23, 26, 25)

plot(temps, type = "o",

     col = "red",

     lwd = 2, 

     main = "Weekly Temperature",

     xlab = "Day",

     ylab = "Temp (C)",

     xlim=c(1,8),

     ylim=c(10,30),

     lty="dotted",

     cex=0.6, #size of dot

     pch=5)  #different symbol in range 1-25

Solution:-

Explanation:-

All parameter of plot():-

Parameter	Purpose	Accepted Values
type	Specifies plot style	“l” (line), “p” (points), “o” (both overlaid), “b” (both separate), “h” (histogram like vertical line)
col	Color of the line	Color name (eg “blue”) or hex code
bg	Background color	“bg” only work with pch value between 21-25 or “bg” use with par(bg “color name” )
lty	Line type	1: solid (default), 2:dashed, 3:dotted, 4:dot-dash, 5:long-dash
lwd	Line width	Numerical value; 2 is twice the default thickness
main	Title of the chart	A text string
sub	Subtitle	A subtitle displayed below x-axis
asp	y/x aspect ratio	If asp=1 then x-axis equal to y-axis, If asp=2 then y-axis more than x-axis
xlab/ ylab	Axis labels	Text string for the X and Y axes
xlim/ ylim	Axis limits	A vector of two values: c(min,max)
pch	Point shape	Integer 0-25 (used when type= “o” or “b”)
cex	Point/ text size	Numerical value (default is 1)
log	Applied logarithmic scaling to the axes	“x”, “y”, or “xy”
axes	Determines if the default axis lines and tick marks are drawn	TRUE (default) or FALSE
frame.plot	Draw a border box around the right and top plot area	TRUE or FALSE
las	Control the orientation of axis	0 (parallel), 1 (horizontal), 2 (perpendicular), 3 (vertical)
ann	Determine if titles and axis labels are shown	TRUE or FALSE
panel.first	Executes an expression (like a grid) before points are drawn	Any plotting expression (eg. grid(), abline()
panel.list	Executes an expression after the points are drawn	Any plotting expression

Example-2:- If we have multiple line in question then-- y1 <- c(2, 4, 6, 8, 10),

y2 <- c(1, 3, 5, 7, 9),  y3 <- c(5, 4, 3, 2, 1)

Code:-

# Define your data 

y1 <- c(2, 4, 6, 8, 10)

y2 <- c(1, 3, 5, 7, 9)

y3 <- c(5, 4, 3, 2, 1)

# Create the main plot

plot(y1, type="b", col="blue", pch=16, ylim=c(0, 10), ylab="Value", main="Base R Plot")

#If we have to add more line then we use only line command instead of plot

lines (y2, type="b", col="red", pch=17)

lines (y3, type="b", col="green", pch=18)

# Add a legend

legend=c("y1", "y2", "y3"),  col=c("blue", "red", "green"), pch=16:18, lty=1, 

      inset=c(-0.35, 0), cex=0.8) 

Solution:-

Explanation:-

• In 2nd, 3rd, 4th line we just put the data which given in question
• To add the line first we use plot command, as you can see above I explain all the parameter in a table , pch= mainly for different symbol (Put value in between 1-25) 
• To add more line then we use only "lines" command instead of plot here
• In last command we use legend to create a seperate box to show the data, but when you try to put the legend box out of the main box it not appear (see next example)

Example-3:- Problem in put the legend box out of the main box

Code:-

# Define your data 

y1 <- c(2, 4, 6, 8, 10)

y2 <- c(1, 3, 5, 7, 9)

y3 <- c(5, 4, 3, 2, 1)

# Create the main plot

plot(y1, type="b", col="blue", pch=16, ylim=c(0, 10), ylab="Value", main="Base R Plot")

#If we have to add more line then we use only line command instead of plot

lines (y2, type="b", col="red", pch=17)

lines (y3, type="b", col="green", pch=18)

# Add a legend

legend=c("y1", "y2", "y3"),  col=c("blue", "red", "green"), pch=16:18, lty=1, 

      inset=c(-0.02, 0.4), cex=0.5) 

Result:-

Explanation:- As you can see here when have change the inset value, legend box not seen completely. To fix this problem we use par(xpd=TRUE) , check in next example

Example-4:- Legend box out of the main box 

Code:-

# Define your data 

y1 <- c(2, 4, 6, 8, 10)

y2 <- c(1, 3, 5, 7, 9)

y3 <- c(5, 4, 3, 2, 1)

# Create the main plot

plot(y1, type="b", col="blue", pch=16, ylim=c(0, 10), ylab="Value", main="Base R Plot")

# If want to put legend box out of the main box 

par(xpd=TRUE)

#If we have to add more line then we use only line command instead of plot

lines (y2, type="b", col="red", pch=17)

lines (y3, type="b", col="green", pch=18)

# Add a legend

legend=c("y1", "y2", "y3"),  col=c("blue", "red", "green"), pch=16:18, lty=1, 

      inset=c(-0.02, 0.4), cex=0.5) 

Result:-

Explanation:- In this we use par(xpd=TRUE) to visualize the legend box out of the main box, but you see one problem here that space on the right side is not so much that I put legend box. So, either I have to decrease the font size of legend box by cex command (but that cause font size small and difficult to visualize) or we use par (mar=c ()) command see in next example

Example-5:- To create more space or more data 

Code:-

y1 <- c(2, 4, 6, 8, 10)

y2 <- c(1, 3, 5, 7, 9)

y3 <- c(5, 4, 3, 2, 1)

# Create the main plot

plot(y1, type="b", col="blue", pch=16, ylim=c(0, 10), ylab="Value", main="Base R Plot")

# If want to put legend box out of the main box 

par(xpd=TRUE)

# If you want space on right side as you can see in the image there is no space to put legend box out of the main box

par(mar=c(2, 2, 2, 4) +0.1)

#If we have to add more line then we use only line command instead of plot

lines (y2, type="b", col="red", pch=17)

lines (y3, type="b", col="green", pch=18)

# Add a legend

legend=c("y1", "y2", "y3"),  col=c("blue", "red", "green"), pch=16:18, lty=1, 

      inset=c(-0.02, 0.4), cex=0.5) 

Result:-

Explanation:-

The command par(mar=c(2, 2, 2, 4) +0.1)

Value	Margin	Description
2	Bottom	Sets the bottom margin to approximately 2.1 lines of text (usually use for label x-axis) if space not present
2	Left	Sets the left margin to approximately 2.1 lines (usually use for label y-axis)
2	Top	Sets the top margin to approximately 2.1 lines (usually for the main plot title)
4	Right	Sets the right margin to approximately 4.1 line of text

• 0.1 in last is optional you can avoid this
• As you can see "4" in par(mar=c(2,2,2,4) denote the right side , which create space in the right side of image so you put legend box in that space