Animated Line Graphs

Line graphs can be very useful indicators of data. Animating them draws your viewer in and grabs their attention.

For all of the basic animations, we'll use the txhousing dataset within the ggplot2 library, for simplicity. This dataset contains "information about the housing market in Texas provided by the TAMU real estate center".

In a few minutes, we'll make this graph:

---

To get started, let's load all the libraries we'll need:

library(ggplot2) #plotting and getting the txhousing dataset
library(dplyr) #sorting the data to fit our graph
library(gganimate) #animating the ggplot

Now that we have the libraries, we can get the dataset. So that we can easily view it, let's put it into a variable.

txhousing_data <- txhousing

We want to have a single number for sales and listings for each month and year. Luckily, the dataset already comes with a date column that specifies both the month and the year, so we can just group based on date and sum the sales and listings for every city to get a total.

txhousing_data <- txhousing_data |> 
  group_by(date) |> 
  filter(!is.na(sales)) |> #any NAs make the 'sum' = 0
  filter(!is.na(listings)) |> #any NAs make the 'sum' = 0
  summarise(
    sales = sum(sales),
    listings = sum(listings)
  )

Let's look at the data now.

Now that the data is in the right format, we're ready to plot. We'll start by first generating a static line graph, with the date on the x-axis and sales/listings on the y-axis (in two separate lines).

ggplot(txhousing_data)+
  geom_line(aes(x=date, y=sales, color="Sales"))+
  geom_line(aes(x=date, y=listings, color="Listings"))

This doesn't look too pretty, so let's add a theme, some nicer colors, and fix the labels.

ggplot(txhousing_data)+
  geom_line(aes(x=date, y=sales, color="Sales"))+
  geom_line(aes(x=date, y=listings, color="Listings"))+
  scale_color_manual(breaks = c("Sales", "Listings"), values=c("#1f948b","#482071"))+
  scale_y_continuous(label=scales::comma)+ #requires 'scales' has been installed
  theme_minimal()+
  labs(title="Texas Housing Market from 2000-2015",
       subtitle="House sales are cyclical and somewhat consistent, listings are more volatile.",
       color="",
       x="Year",
       y="Number of Sales/Listings")+
  theme(plot.title = ggtext::element_markdown(size = 22, hjust =0.5, face = "bold"),  #requires the ggtext package is installed
        plot.subtitle = ggtext::element_markdown(size = 15, hjust =0.5, face = "bold")) #requires the ggtext package is installed

We're almost there. To convert this into an animation we have to add transition_reveal(date) to the end of our code. transition_reveal is somewhat self-explanatory: we want to reveal more and more of the line as animation goes on. Here, date is what is actually moving the animation. Essentially, we're telling the computer to reveal more and more of each line as the date increases.

ggplot(txhousing_data)+
  geom_line(aes(x=date, y=sales, color="Sales"))+
  geom_line(aes(x=date, y=listings, color="Listings"))+
  scale_color_manual(breaks = c("Sales", "Listings"), values=c("#1f948b","#482071"))+
  scale_y_continuous(label=scales::comma)+
  theme_minimal()+
  labs(title="Texas Housing Market from 2000-2015",
       subtitle="House sales are cyclical and somewhat consistent, listings are more volatile.",
       color="",
       x="Year",
       y="Number of Sales/Listings")+
  theme(plot.title = ggtext::element_markdown(size = 22, hjust =0.5, face = "bold"),  #requires the 'ggtext' package is installed
        plot.subtitle = ggtext::element_markdown(size = 15, hjust =0.5, face = "bold"))+ #requires the 'ggtext' package is installed  
  transition_reveal(date) #new line added

The animation is now in place, but the text is cut off and the resolution isn't ideal. To fix this we put our animation into an object using the assignment operation (<-) and then call animate() on that object, with some self-explanatory parameters.

animation <- ggplot(txhousing_data)+ #added the pipe into 'animation'
  geom_line(aes(x=date, y=sales, color="Sales"))+
  geom_line(aes(x=date, y=listings, color="Listings"))+
  #continues from above code snippet

animate(animation, fps=10, duration=15, end_pause=9, width = 9, height = 8,
         units = "in", res = 200)

We're animating our animation, with 10 frames per second for 15 seconds. The animation's last 9 frames will pause before it wraps back around (end_pause). The width and height are 9 and 8 inches each and the resolution (res) or how many pixels will be in each inch, is 200 (i.e. the final animation will be 1800x1600 pixels).

When you run the animation() function, it should automatically pop up in the "Viewer" tab in R. From there, you can open it in a new window and save it as a GIF from there. However, if you want to easily save it to your local directory within R, simple change some syntax:

animation <- animate(animation, fps=10, duration=15, end_pause=9, height = 8,
        width = 9, units = "in", res = 200)

anim_save('animation.gif', animation)

Essentially, we're giving the animation its own specifications for animating, so that it can export seamlessly. If you're having trouble exporting or saving your chart, make sure that the package "gifski" is installed.

That's it! You've now successfully made an animated line chart.

Click here to view the raw file used to make this animation.