Legend control in R Programming - Mini Project: Build & Apply

Legend control

📖 Scenario: You are creating a simple scatter plot to compare two groups of data points. You want to add a legend to clearly show which color represents which group.

🎯 Goal: Build a scatter plot with two groups of points and add a legend that correctly labels each group.

📋 What You'll Learn

Create two numeric vectors called group1 and group2 with the exact values specified.

Create a vector called labels with the exact group names.

Plot the points for both groups with different colors.

Add a legend that uses the labels vector and matches the colors used in the plot.

💡 Why This Matters

🌍 Real World

Legends help people understand what different colors or symbols mean in charts, like showing sales by region or comparing groups in a study.

💼 Career

Data analysts and scientists often create plots with legends to communicate insights clearly to others.

1

DATA SETUP: Create data vectors

Create two numeric vectors called group1 with values c(2, 4, 6, 8) and group2 with values c(1, 3, 5, 7).

R Programming

# Create the vectors group1 and group2
# Your code here

Need a hint?

Use the c() function to create numeric vectors with the exact values.

2

CONFIGURATION: Create labels vector

Create a character vector called labels with the exact values c("Group A", "Group B").

R Programming

group1 <- c(2, 4, 6, 8)
group2 <- c(1, 3, 5, 7)
# Create the labels vector
# Your code here

Need a hint?

Use c() to create a character vector with the exact group names.

3

CORE LOGIC: Plot points with colors

Use plot() to plot group1 points in red with pch=16. Then add group2 points in blue using points() with pch=17.

R Programming

group1 <- c(2, 4, 6, 8)
group2 <- c(1, 3, 5, 7)
labels <- c("Group A", "Group B")
# Plot group1 points in red
# Add group2 points in blue
# Your code here

Need a hint?

Use plot() for the first group and points() to add the second group with different colors and symbols.

4

OUTPUT: Add legend to the plot

Add a legend to the top right of the plot using legend() with labels, colors c("red", "blue"), and point characters c(16, 17).

R Programming

group1 <- c(2, 4, 6, 8)
group2 <- c(1, 3, 5, 7)
labels <- c("Group A", "Group B")
plot(group1, rep(1, length(group1)), col = "red", pch = 16, xlim = c(0, 10), ylim = c(0.5, 1.5), ylab = "", xlab = "Value", yaxt = "n")
points(group2, rep(1.2, length(group2)), col = "blue", pch = 17)
# Add a legend to the top right
# Your code here

Need a hint?

Use legend() with the exact parameters to match colors and symbols to the labels.