Here is a similar example using data from Iceland https://www.covid.is/data.
You have a Date column and a Number column with infections.
Step 1 – Highlight both columns
Step 2 – Select Add Bar under the command menu.
This gives you a simple bar graph with a date axis. Here we have added formatting to remove the lines and add a fill color.
The Hover tool is also turned on so you can hover over a bar and see the value.
Turn on the Hover using shift-command-H.
You could also add the other elements of the graph – showing items on the time line.
Currently, we don’t have a way for you to display the hover on a web page. Just within DataGraph. They could have done this graphic using the D3 JavaScript library or there are Plotly libraries for R that can create interactive graphs like this.
Are you looking for the ability to produce a graph with hover elements on a web page?