Saving the Displayed Graph in R
Saving your plotted graphs is essential for sharing results and including visuals in reports. Here’s a detailed guide on how to save the displayed graph in R.
General Steps for Saving Graphs
To save a graph in R, you need to:
- Open a Graphics Device: Specify the type of file and output settings.
- Plot the Graph: Use plotting functions like plot(), ggplot(), etc.
- Close the Graphics Device: Save and close the file.
Types of File Formats and Corresponding Functions
Creates a PDF file, suitable for printed or digital documents.
Example: Save a Graph as a PDF
pdf("graph.pdf", width = 8, height = 6) # Opens a PDF device
plot(1:10, (1:10)^2, main = "Example PDF Graph", xlab = "x", ylab = "y")
dev.off() # Closes the device and saves the file
- width and height: Dimensions of the graph in inches.
PNG
Creates a PNG file, a raster format ideal for web images and presentations.
Example: Save a Graph as a PNG
png("graph.png", width = 800, height = 600, res = 100) # Opens a PNG device
plot(1:10, (1:10)^2, main = "Example PNG Graph", xlab = "x", ylab = "y")
dev.off() # Closes the device and saves the file
- width and height: Dimensions of the graph in pixels.
- res: Resolution in dots per inch (DPI).
JPEG
Creates a JPEG file, often used for web images and presentations.
Example: Save a Graph as a JPEG
jpeg("graph.jpeg", width = 800, height = 600, quality = 90) # Opens a JPEG device
plot(1:10, (1:10)^2, main = "Example JPEG Graph", xlab = "x", ylab = "y")
dev.off() # Closes the device and saves the file
- quality: Compression quality (0 to 100).
TIFF
Creates a TIFF file, often used for high-quality images in scientific publications.
Example: Save a Graph as a TIFF
tiff("graph.tiff", width = 800, height = 600, res = 300) # Opens a TIFF device
plot(1:10, (1:10)^2, main = "Example TIFF Graph", xlab = "x", ylab = "y")
dev.off() # Closes the device and saves the file
- res: Resolution in DPI.
Common Parameters for File Devices
- width and height: Control the size of the graph.
- res: Controls the resolution for raster formats (PNG, JPEG, TIFF).
- bg: Background color of the graph (for raster formats).
Advanced Methods for Saving Graphs
Multiple Plots in One File
To save multiple plots in a single file, use par() to configure the layout.
Example: Multiple Plots in a PDF
pdf("multiple_plots.pdf")
par(mfrow = c(2, 2)) # Layout for 2x2 plots
plot(1:10, (1:10)^2, main = "Plot 1")
plot(10:1, (1:10)^2, main = "Plot 2")
plot(1:10, (1:10)^3, main = "Plot 3")
plot((1:10)^2, (1:10)^3, main = "Plot 4")
dev.off()
Using ggsave() for ggplot2
If you use ggplot2, the ggsave() function simplifies saving graphs.
Example: Save with ggsave()
library(ggplot2)
p <- ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point()
ggsave("ggplot_graph.png", plot = p, width = 8, height = 6, dpi = 100)
- plot: The graph to save.
- width and height: Dimensions of the file in inches.
- dpi: Resolution in DPI.
Saving Graphs in R Markdown
In R Markdown, graphs are automatically saved in the specified format in the document.
Example: R Markdown with Graphs
```{r}
plot(1:10, (1:10)^2, main = "Graph in R Markdown")
Graphs will be saved in the format specified by the options in the R Markdown document.
Summary
- Open a File Device**: Use `pdf()`, `png()`, `jpeg()`, `tiff()` to specify the format and settings.
- Plot the Graph**: Use plotting functions like `plot()`, `ggplot()`, etc.
- Close the Device**: Use `dev.off()` to save and close the file.
- Customize Settings**: Adjust size, resolution, and background color as needed.
- Advanced Methods**: Save multiple plots in one file or use `ggsave()` for `ggplot2`.