A bidirectional chart, also known as a two-sided bar chart, is used to compare two (rarely more) sets of data side by side along the horizontal axis. Unlike other similar charts, such as the divergent chart (butterfly, mirror, tornado, etc.) and the Likert scale chart, the bidirectional histogram bars start on opposite sides and are directed toward each other.

To compare two different sets of data, you can create a side-by-side bar chart in Excel, also known as a double chart. It is most informative to compare data in the presence of two identical coordinate grids with the same vertical and horizontal axes:

To compare two sets of data, you can create various comparison charts, such as a butterfly chart, mirror chart, tornado chart, etc., or a double-sided chart. However, comparing the values in opposite directions is not always convenient. In order to display two datasets, you can use Excel to create a side-by-side bar chart, also known as a double bar chart.

The tornado chart is a modified version of bar charts with two columns of data series whose bars are horizontal and pointing in opposite directions, with the base in the middle of the chart. In fact, the only difference between the tornado chart and the very similar charts - the butterfly chart and the mirror chart - is that the data series used to create the tornado chart must be sorted from the largest to the smallest.

A mirror bar chart or double bar chart is a special type of bar chart (actually, a simplified version of a diverging chart referred to as a comparative histogram) that displays two sets of data comparatively side by side along the vertical axis. The chart resembles a reflection of a mirror, hence the name "mirror bar chart":

A butterfly chart is a simplified version of a diverging chart, also known as a divergent chart. Unlike a diverging chart, a butterfly chart can only compare two data sets using two horizontal bars with a central baseline.

When creating comparison charts, two different approaches are used:
- comparative analysis of some parameters of one key element - the favorite one (product, brand, etc.) with the parameters of competitive elements (products, brands, etc.),
- comparison of the parameters of a certain list of elements without favorites.

Nowadays, icons, logos, and abbreviations often carry more information than the textual names of companies, brands, applications, games, etc. To create memorable charts and faster understanding and recognition of information, instead of the names of countries, brands, etc., you can substitute the corresponding pictures on the axis of the charts.

It is often necessary to visualize the results of voting or polls in which the answers belong to different scales. For example, when collecting data on preferences, such as choosing from the proposed persons, teams (parties); applications, browsers; gadget models; food, colors; etc. See how to organize a team color preferences survey in Outlook.

Diverging stacked bar charts, also known as centered stacked bar charts, are widely used to display the results of surveys, polls, or questionnaires analyzed through a ranking scale such as a Likert or numeric scale.