Visualizing Data in R with Default Package:
Curve and RColorBrewer

Draw in Curve in R

The curve() function in R is used to plot mathematical functions over a specified interval.

It’s particularly useful for visualizing the shape of a function or for adding function curves to existing plots.

The curve() function is a powerful tool for visualizing mathematical expressions and functions directly in R.

Example 1: Plotting a Simple Function

Let’s plot the function $y = x^2$ over the interval [-10, 10].

Note: If we want to hide the box around the graph, we can set the argument bty = "n".

Example 2: Adding a Curve to an Existing Plot

You can add a curve to an existing plot by setting

add = TRUE.

Example 3: Plotting a Custom Function

You can also plot a custom function using the curve() function.

In R, the lty argument is used in plotting functions to specify the line type, such as solid, dashed, or dotted.

Draw the curve from 10 functions

Exercise 1: Basic Curve Plotting

# Plot y = x^2 over the interval [-10, 10]
curve(x^2, from = -10, to = 10, 
      xlab = "x values", 
      ylab = "y values", 
      main = "Plot of y = x^2")

Objective: Plot a simple mathematical function.

• Use the curve() function to plot the function $y = x^2$ over the interval $[-10, 10]$.

• Label the x-axis as “x values” and the y-axis as “y values”.

• Add a main title to the plot that says “Plot of y = x^2”.

Exercise 2: Adding Multiple Curves

# Plot y = x^2 and y = x^3 on the same graph
curve(x^2, from = -5, to = 5, 
      col = "blue", 
      lty = 1, 
      ylab = "y values", 
      main = "Plot of y = x^2 and y = x^3")
curve(x^3, from = -5, to = 5, 
      col = "red", 
      lty = 2, 
      add = TRUE)

# Add a legend
legend("topleft", legend = c("y = x^2", "y = x^3"), 
       col = c("blue", "red"), 
       lty = 1:2)

Objective: Overlay multiple curves on the same plot.

• Use the curve() function to plot $y = x^2$ and $y = x^3$ on the same graph over the interval $[-5, 5]$.

• Use different colors and line types for each curve.

• Add a legend to distinguish between the two curves.

Exercise 3: Plotting a Custom Function

# Plot the custom function over the interval [0, 20]
curve(sin(x) * exp(-0.1 * x), from = 0, to = 20, 
      col = "blue", 
      lty = 2, 
      ylab = "f(x)", 
      main = "Plot of f(x) = sin(x) * exp(-0.1x)")

Objective: Create and plot a custom function.

• Define a custom function in R, say $f(x) = \sin(x) \times \exp(-0.1x)$.

• Use the curve() function to plot this custom function over the interval $[0, 20]$.

• Use a dashed line type and a blue color for the plot.

Exercise 4: Exploring Different Intervals

# Plot y = log(x) over different intervals
curve(log(x), from = 0.1, to = 10, 
      col = "blue", 
      ylab = "log(x)", 
      main = "Plot of y = log(x) over different intervals")
curve(log(x), from = 1, to = 100, 
      col = "red", 
      add = TRUE)
curve(log(x), from = 10, to = 1000, 
      col = "green", 
      add = TRUE)

# Add a legend
legend("topleft", legend = c("[0.1, 10]", "[1, 100]", "[10, 1000]"), 
       col = c("blue", "red", "green"), 
       lty = 1)

Objective: Understand the impact of different intervals.

• Plot the function $y = \log(x)$ using the curve() function over three different intervals: $[0.1, 10]$, $[1, 100]$, and $[10, 1000]$.

• Plot all three curves on the same graph using different colors.

• Add a legend to explain which color corresponds to which interval.

Exercise 5: Adding Points and Annotations

# Plot y = sqrt(x) over the interval [0, 25]
curve(sqrt(x), from = 0, to = 25, 
      col = "purple", 
      ylab = "sqrt(x)", 
      main = "Plot of y = sqrt(x) with points and annotations")

# Add points at x = 5, 10, 15, 20
points(c(5, 10, 15, 20), sqrt(c(5, 10, 15, 20)), 
       pch = 19, 
       col = "red")

# Annotate each point with (x, y) values
text(c(5, 10, 15, 20), sqrt(c(5, 10, 15, 20)) + 0.5, 
     labels = c("(5, sqrt(5))", "(10, sqrt(10))", 
                "(15, sqrt(15))", "(20, sqrt(20))"), 
     pos = 3)

Objective: Enhance the plot with points (point() function) and annotations (text() function).

• Use the curve() function to plot the function $y = \sqrt{x}$ over the interval $[0, 25]$.

• Add points at $x = 5, 10, 15,$ and $20$ on the curve.

• Annotate each point with its corresponding $(x, y)$ value.

• Add a title, and label the axes accordingly.

The package RColorBrewer

RColorBrewer is an R package that provides a set of color palettes for use in R graphics.

It is especially useful for creating visually appealing and colorblind-friendly plots.

The palettes in RColorBrewer are designed to be used with categorical, sequential, or diverging data.

Displaying All Palettes

This will show you all available color palettes in the package, organized by type (sequential, diverging, qualitative).

Using a Specific Palette