tmap save map graph in r

Lussy04

3 min read

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25-01-2025

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The tmap package in R is a powerful tool for creating visually appealing and informative maps. But creating a beautiful map is only half the battle. Knowing how to save your work in various formats is crucial. This guide provides a comprehensive walkthrough of different methods for saving tmap map graphs in R, covering various file types and resolutions. We'll cover saving your TMAP map graphs as PNG, JPG, PDF, and SVG formats.

Understanding tmap_save()

The primary function for saving tmap maps is tmap_save(). This function offers flexibility in controlling the output format, resolution, and file size of your saved map.

Basic Usage:

The most straightforward way to save a tmap map is using the tmap_save() function. This function takes the map object as the first argument and the file path as the second argument.

library(tmap)

# Assuming 'tm1' is your tmap object
tmap_save(tm1, "my_map.png")

This saves the map as a PNG file named "my_map.png" in your current working directory. You can easily change the filename and directory as needed.

Specifying File Formats and Resolutions

tmap_save() allows you to control the file type and resolution. Let's explore some common formats and options:

Saving as PNG:

PNG is a lossless format suitable for maps with sharp lines and text. You can adjust the resolution using the width and height arguments (in pixels).

tmap_save(tm1, "my_map_highres.png", width = 1200, height = 800)

This creates a high-resolution PNG image. Experiment with different width and height values to find the optimal balance between image quality and file size.

Saving as JPG:

JPG is a lossy format that results in smaller file sizes but can lead to some loss of image quality, particularly in areas with sharp contrasts.

tmap_save(tm1, "my_map.jpg", width = 1200, height = 800)

Saving as PDF:

PDF is a vector format, making it ideal for maps that need to be scaled without losing quality. This is particularly useful for publication or printing.

tmap_save(tm1, "my_map.pdf", width = 12, height = 8, units = "in")

Note the use of units = "in" here. This sets the dimensions in inches, which is common for print publications. Adjust the width and height to your desired dimensions.

Saving as SVG:

Scalable Vector Graphics (SVG) is another vector format offering high-quality, scalable images. It's well-suited for web use.

tmap_save(tm1, "my_map.svg")

Advanced Options

tmap_save() provides several additional parameters for fine-tuning the output:

• dpi: Sets the dots per inch (DPI) resolution for raster formats (PNG, JPG). Higher DPI means higher resolution.
• units: Specifies the units for width and height (e.g., "in", "cm", "px").
• asp: Controls the aspect ratio of the map.

Example: Creating and Saving a TMAP Map

Let's illustrate with a simple example:

library(tmap)
library(sf)

# Load example data (replace with your own data)
data("World")

# Create a simple tmap
tm1 <- tm_shape(World) +
  tm_polygons("pop_est", style = "jenks", palette = "YlOrRd") +
  tm_layout(title = "World Population")

# Save the map in different formats
tmap_save(tm1, "world_pop_png.png", width = 800, height = 600)
tmap_save(tm1, "world_pop_pdf.pdf", width = 8, height = 6, units = "in")
tmap_save(tm1, "world_pop_svg.svg")

This code snippet creates a map showing world population and saves it as PNG, PDF, and SVG files. Remember to install the necessary packages (tmap and sf) if you haven't already.

Troubleshooting and Best Practices

• Ensure Packages are Installed: Make sure you have the tmap package installed (install.packages("tmap")).
• Specify File Paths: If you want to save the map to a specific directory, provide the full file path.
• Experiment with Resolution: Adjust the width, height, and dpi parameters to find the best balance between image quality and file size.
• Choose the Right Format: Consider the intended use of the map when selecting a file format. PDF or SVG are generally preferred for publication or when scalability is important. PNG is a good all-around choice for online use.

By mastering these techniques, you can effectively save your tmap creations in the desired format and resolution, ensuring your maps are ready for sharing, publication, or inclusion in reports. Remember to always experiment and find the settings that best suit your needs and the intended use of your map.