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