2 dimension + 1 metric
Adds a dimension to the bar chart, represented by a group of bars or one « cut » bar on the dimension of the horizontal axis.
Stacked mode allows you to effectively observe the evolution of the sum of elements of a dimension, over the dimension of the x-axis (example: time), and gives you an idea of the distribution of elements within that dimension.
Grouped mode effectively compares the parallel evolutions of each element of the dimension which is shown by a group of bars.
A simple example
Let's say you want to split your visits over time by type of referral. You want to see on a day-to-day basis if your visits are direct from search engines or from other websites to which your website is linked.
Try it with your own data on the Visualization Playground
Let's analyze a bit
At first glance it’s clear that visits from search engines vary little over time, as opposed to direct visits or referrals, which vary quite a bit more and display an almost parallel evolution.
If we switch to stacked mode, we can see that the proportion between direct visits and referrals is regular over time.
What does this mean? That your visitors already know how to access your website, whether it be by typing the URL or because they know where to find a link?