Week 3 Discussion: Exercise

Note

It’s up to you to organize your own week3-discussion.qmd file (i.e. there is no template). You may (should) discuss and work through today’s exercise with a partner (or two!).

Example 1: {palmerpenguins} ggplot

1. Copy the following code into your week3-discussion.qmd file and add code chunk options that:
   • render the output (i.e. plot), but not the code
   • suppress any warnings or messages
2. Add alt text using the fig-alt: code chunk option
3. “Inspect” your plot (right click > Inspect) to verify that the alt attribute and text is added to the HTML

library(ggplot2)
library(palmerpenguins)

ggplot(data = penguins, aes(x = body_mass_g, fill = species)) +
  geom_histogram(alpha = 0.5, 
                 position = "identity") +
  scale_fill_manual(values = c("darkorange","purple","cyan4")) +
  labs(x = "Body mass (g)",
       y = "Frequency",
       title = "Penguin body masses")

Example 2 (from The New York Times):

1. Download this viz (right click > Save Image As… > save to your class repo)
2. Embed the viz in week3-discussion.qmd using Markdown syntax and add alt text:

![](file/path/to/your/image){fig-alt="Alt text goes here"}

3. “Inspect” your image (right click > Inspect) to verify that the alt attribute and text is added to the HTML

Note

This graphic form is called a dot plot.

Dot plots are particularly useful for visualizing variability within a single measured numerical variable – here, that’s how much temperature deviates from the 20th-century average for each month in a given year. Year is treated as a categorical variable.

It’s easy to confuse dot plots with scatter plots, which alternatively are used to visualize a relationship between two (or sometimes three) numeric variables.

Example 3 (Fig 1A from Chapman et al. 2024):

1. Download this viz (right click > Save Image As… > save to your class repo)
2. Embed the viz in week3-discussion.qmd using HTML syntax and add alt text (you’ll also need to include the width attribute to make the image a bit smaller):

<img src="file/path/to/image" alt="Alt text goes here" width="700px">

3. “Inspect” your image (right click > Inspect) to verify that the alt attribute and text is added to the HTML

Note

The associated figure caption for this figure:

The >2.6 billion species observations in the Global Biodiversity Information Facility (GBIF) database are disproportionately from high-income countries.

Example 4 (Write alt text for a viz of your choice)

1. Save and embed a data viz of your choice using Markdown or HTML syntax
2. Add alt text
3. Share and discuss your alt text with a partner / group