Animation is surprisingly easy. The sliderInput() function, which gives an HTML widget that allows the selection of a number along a line, has an optional animation function that will increment a variable by a set amount every time a specified unit of time elapses. This allows you to very easily produce a graphic that animates.

In the following example, we are going to look at the monthly graph and plot a linear trend line through the first 20% of the data (0–20% of the data). Then, we are going to increment the percentage value that selects the portion of the data by 5% and plot a linear through that portion of data (5–25% of the data). Then, increment again 10–30% and plot another line, and so on.

There is a static image in the following screenshot:

The slider input is set up as follows, with an ID, label, minimum value, maximum value, initial value, step between values, and the animation options, giving the delay in milliseconds and whether the animation should loop:

sliderInput...