The text() Function
Basic Usage
The text() function adds text to an existing plot at specified coordinates.
Basic Syntax:
text(x, y, labels, pos, offset, cex, col, font)
- x: The x-coordinate where the text will be placed.
- y: The y-coordinate where the text will be placed.
- labels: The text to display.
- pos: The position of the text relative to the coordinates (1 for below, 2 for left, 3 for above, 4 for right).
- offset: Offset of the text from the specified coordinates.
- cex: Expansion factor to adjust the text size.
- col: Color of the text.
- font: Font style (1 for normal, 2 for bold, 3 for italic, 4 for underline).
Example:
# Create a basic plot x <- 1:10 y <- x^2 plot(x, y, main = "Text Annotation Example", xlab = "X", ylab = "Y") # Add text text(5, 25, "Important Point", cex = 1.2, col = "red", pos = 4)
- text(5, 25, “Important Point”, …): Places the text “Important Point” at coordinates (5, 25).
- cex = 1.2: Increases the text size.
- col = “red”: Sets the text color to red.
- pos = 4: Places the text to the right of the coordinates.
Adding Text to Specific Points
You can use text() to label specific points on the plot.
Example:
# Create a basic plot
plot(x, y, main = "Text on Specific Points", xlab = "X", ylab = "Y")
# Add text for each point
text(x, y, labels = paste("(", x, ",", y, ")", sep = ""), pos = 1, cex = 0.8)
- labels = paste(“(“, x, “,”, y, “)”, sep = “”): Creates labels with the coordinates of the points.
- pos = 1: Places the text below the coordinates of the points.
Adjusting Text Size and Position
Use cex and pos to adjust the text size and position.
Example:
# Create a basic plot plot(x, y, main = "Adjust Text Size and Position", xlab = "X", ylab = "Y") # Add text with different sizes and positions text(5, 25, "Large Text", cex = 2, col = "blue", pos = 3) # Larger text above text(7, 50, "Small Text", cex = 0.6, col = "green", pos = 1) # Smaller text below
- cex = 2: Increases the text size.
- cex = 0.6: Decreases the text size.
Using Text for Annotations
Add text annotations to highlight specific parts of the plot, such as points of interest or key observations.
Example:
# Create a basic plot plot(x, y, main = "Annotations with Text", xlab = "X", ylab = "Y") # Add an annotation text(8, 64, "Maximal Here", cex = 1.5, col = "darkred", pos = 3, font = 2)
- font = 2: Makes the text bold.
- pos = 3: Places the text above the specified point.
Adding Text in Relative Coordinates
You can place text using relative coordinates for proportional positioning.
Example:
# Create a basic plot plot(x, y, main = "Text in Relative Coordinates", xlab = "X", ylab = "Y") # Add text with relative coordinates text(x = max(x) * 0.5, y = max(y) * 0.5, "Central Text", cex = 1.2, col = "purple")
- x = max(x) * 0.5: Places the text at the midpoint of the x-axis.
- y = max(y) * 0.5: Places the text at the midpoint of the y-axis.
Summary
- Basic Usage: Use text() to add text at specified coordinates on a plot.
- Text on Points: Label specific points with coordinates.
- Adjust Size and Position: Modify text size (cex) and position (pos).
- Annotations: Use text() to annotate parts of the plot or highlight key points.
- Relative Coordinates: Place text using proportional coordinates for dynamic positioning.