Add and customize titles

How this chapter is organized?

• Change main title and axis labels
• title colors
• The font style for titles
• Change the font size
• Use the title() function
• Customize the titles using par() function.

Read more —> Add titles to a plot in R software.

Plot titles can be specified either directly to the plotting functions during the plot creation or by using the title() function (to add titles on an existing plot).

# Add titles
barplot(c(2,5), main="Main title",
        xlab="X axis title",
        ylab="Y axis title",
        sub="Sub-title",
        col.main="red", col.lab="blue", col.sub="black")
# Increase the size of titles
barplot(c(2,5), main="Main title",
        xlab="X axis title",
        ylab="Y axis title",
        sub="Sub-title",
        cex.main=2, cex.lab=1.7, cex.sub=1.2)

Read more —> Add titles to a plot in R software.

Add legends

How this chapter is organized?

• R legend function
• Title, text font and background color of the legend box
• Border of the legend box
• Specify legend position by keywords

Read more —> Add legends to plots

The legend() function can be used. A simplified format is :

legend(x, y=NULL, legend, col)

# Generate some data
x<-1:10; y1=x*x; y2=2*y1
# First line plot
plot(x, y1, type="b", pch=19, col="red", xlab="x", ylab="y")
# Add a second line
lines(x, y2, pch=18, col="blue", type="b", lty=2)
# Add legends
legend("topleft", legend=c("Line 1", "Line 2"),
       col=c("red", "blue"), lty=1:2, cex=0.8)

Read more —> Add legends to plots

Add texts

How this chapter is organized?

• Add texts within the graph
• Add text in the margins of the graph
• Add mathematical annotation to a plot

Read more —> Add text to a plot

To add a text to a plot in R, the text() function [to draw a text inside the plotting area] and mtext()[to put a text in one of the four margins of the plot] function can be used.

A simplified format for text() is :

text(x, y, labels)

plot(cars[1:10,], pch=19)
text(cars[1:10,],  row.names(cars[1:10,]), 
     cex=0.65, pos=1,col="red") 

Read more —> Add text to a plot

Add straight lines

How this chapter is organized?

• Add a vertical line
• Add an horizontal line
• Add regression line

Read more —> abline R function : An easy way to add straight lines to a plot using R software

The R function abline() can be used to add straight lines (vertical, horizontal or regression lines) to a graph.

A simplified format is :

abline(a=NULL, b=NULL, h=NULL, v=NULL, ...)

# Add horizontal and vertical lines
#++++++++++++++++++++++++++++++++++
plot(cars, pch=19)
abline(v=15, col="blue") # Add vertical line
# Add horizontal line, change line color, size and type
abline(h=60, col="red", lty=2, lwd=3)
# Fit regression line
#++++++++++++++++++++++++++++++++++
require(stats)
reg<-lm(dist ~ speed, data = cars)
coeff=coefficients(reg)
# equation of the regression line : 
eq = paste0("y = ", round(coeff[2],1), "*x ", round(coeff[1],1))
plot(cars, main=eq, pch=18)
abline(reg, col="blue", lwd=2)

Read more —> abline R function : An easy way to add straight lines to a plot using R software

Add an axis to a plot

axis() function can be used.

A simplified format is :

axis(side, at=NULL, labels=TRUE)

x<-1:4; y=x*x
plot(x, y, pch=18, col="red", type="b",
     frame=FALSE, xaxt="n") # Remove x axis
axis(1, 1:4, LETTERS[1:4], col.axis="blue")
axis(3, col = "darkgreen", lty = 2, lwd = 0.5)
axis(4, col = "violet", col.axis = "dark violet", lwd = 2)

Read more —> Add an axis to a plot with R software.

Change axis scale : minimum, maximum and log scale

xlim and ylim arguments can be used to change the limits for x and y axis. Format : xlim = c(min, max); ylim = c(min, max).

log transformation can be performed using the parameters : log=“x”, log=“y” or log=“xy”.

x<-1:10; y=x*x
plot(x, y) # Simple graph
plot(x, y, xlim=c(1,15), ylim=c(1,150))# Enlarge the scale
plot(x, y, log="y")# Log scale

Read more —> Axis scale in R software : minimum, maximum and log scale.

Customize tick mark labels

• Color, font style and font size of tick mark labels :
• Orientation of tick mark labels
• Hide tick marks
• Change the string rotation of tick mark labels
• Use the par() function

x<-1:10; y<-x*x
# Simple graph
plot(x, y)
# Custom plot : blue text, italic-bold, magnification
plot(x,y, col.axis="blue", font.axis=4, cex.axis=1.5)

Read more —> Customize tick mark labels.

Change plotting symbols

The following points symbols can be used in R :

Point symbols can be changed using the argument pch.

x<-c(2.2, 3, 3.8, 4.5, 7, 8.5, 6.7, 5.5)
y<-c(4, 5.5, 4.5, 9, 11, 15.2, 13.3, 10.5)
# Change plotting symbol using pch
plot(x, y, pch = 19, col="blue")
plot(x, y, pch = 18, col="red")
plot(x, y, pch = 24, cex=2, col="blue", bg="red", lwd=2)

Read more —> R plot pch symbols : The different point shapes available in R.

Change line types

The following line types are available in R :

Line types can be changed using the graphical parameter lty.

x=1:10; y=x*x
plot(x, y, type="l") # Solid line (by default)
plot(x, y, type="l", lty="dashed")# Use dashed line type
plot(x, y, type="l", lty="dashed", lwd=3)# Change line width

Read more —> Line types in R : lty.

Change colors

• Built-in color names in R
• Specifying colors by hexadecimal code
• Using RColorBrewer palettes
• Use Wes Anderson color palettes
• Create a vector of n contiguous colors

Colors can be specified by names (e.g col=red) or with hexadecimal code (e.gcol = “#FFCC00”).

# use color names
barplot(c(2,5), col=c("blue", "red"))
# use hexadecimal color code
barplot(c(2,5), col=c("#009999", "#0000FF"))

Hexadecimal color charts :

(Source: http://www.visibone.com)

RColorBrewer package can also be used to create a nice looking color palettes. Read our article : Colors in R.

Read more —> Colors in R.

Related articles

Click on the following articles to read more.

Plotting symbols in R

Different plotting symbols are available in R. The graphical argument used to specify point shapes is pch.

Line types in R

The argument lty can be used to specify the line type. To change line width, the argument lwd can be used.

Colors in R

Colors can be specified either by name (e.g col = “red”) or as a hexadecimal code (such as col = “#FFCC00”). You can also use other color systems such as ones taken from the RColorBrewer package.

Add titles to a plot

Plot titles can be specified either directly to the plotting functions during the plot creation or by using the title() function (to add titles on an existing plot).

Add legends to plots

To add legends to plots in R, the R legend() function can be used.

Add texts to a plot

To add a text to a plot in R, the text() and mtext() R functions can be used.

Add straight lines

The R function abline() can be used to add vertical, horizontal or regression lines to a graph.

Add an axis to a plot

axis() function can be used to add a secondary axis to a plot.

Change axis scale in R

The goal of this article is to show you how to set x and y axis limites by specifying the minimum and the maximum values of each axis. We’ll also see how to set the log scale.

Infos

This analysis has been performed using R statistical software (ver. 3.2.4).

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