Legend control in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a legend in an R plot?

A legend explains the symbols, colors, or line types used in a plot so the viewer can understand what each element represents.

beginner

How do you add a basic legend to a plot in R?

Use the legend() function, specifying the position, labels, and symbols or colors to match the plot elements.

beginner

What argument in legend() controls the position of the legend?

The x argument controls the position. It can be a keyword like "topright", "bottomleft", or coordinates like c(1,2).

intermediate

How can you change the colors of legend symbols in R?

Use the col argument inside legend() to specify colors matching the plot symbols or lines.

intermediate

What does the pch argument do in the legend() function?

It sets the plotting character (symbol) used in the legend to match the points or symbols shown in the plot.

Which function is used to add a legend to a plot in R?

A plot()

B title()

C legend()

D points()

The legend() function adds a legend to an existing plot.

How do you position a legend at the top right corner of a plot?

A x = "topright"

B x = "bottomleft"

C x = c(0,0)

D x = "center"

Using x = "topright" places the legend at the top right corner.

Which argument controls the colors of symbols in the legend?

A cex

B pch

C lty

D col

The col argument sets the colors of the legend symbols or lines.

If you want the legend symbols to match the plot points, which argument do you set?

A bg

B pch

C lwd

D col

The pch argument sets the plotting character (symbol) in the legend.

Can you specify exact coordinates for the legend position in R?

A Yes, by giving numeric coordinates to the x argument

B No, only keywords like 'topright' are allowed

C Only if you use the plot() function

D Only if you use ggplot2

You can specify exact coordinates like c(x, y) to position the legend precisely.

Explain how to add and customize a legend in a basic R plot.

Think about what you want the legend to show and where it should appear.

Describe the role of the 'pch' and 'col' arguments in the legend() function.

These arguments help the legend look like the plot points or lines.