Tables, Charts, and Fields - Implementing Splunk: Big Data Reporting and Development for Operational Intelligence - page 57

It will create a table like this:
Since there are no numbers, this cannot be directly made into an image, but it is still
a very useful representation of the data.
Using timechart to show values over time
timechart lets us show numerical values over time. It is similar to the chart
command, except that time is always plotted on the x axis. Here are a couple of
things to note:
• The events must have an _time field. If you are simply sending the results
of a search to timechart , this will always be true. If you are using interim
commands, you will need to be mindful of this requirement.
• Time is always "bucketed", meaning that there is no way to draw a point
per event.
Let's see how many errors have been occurring:
sourcetype="impl_splunk_gen" error | timechart count
The default chart will look something like this: