# RGraph: HTML5 canvas graph library - Bar chart

The bar chart is probably one of the most widely used of charts, and also one of the most versatile. It's defined as a chart with rectangular bars with lengths proportional to the values they represent. The bar chart can be used to represent two or more values. With grouped and stacked bar charts, you can visualise two or more sets of data. For example two years worth of sales figures. Doing this you will be able to easily see differences, for example a better year when it comes to sales. You can also show negative values by having the X axis in the center, like the examples shown. If you use a grouped or stacked bar chart, a key may be helpful to your users.

By using the tooltips feature, you can provide more detail about what a particular bar represents. The tooltips in RGraph can contain wide range of HTML, so you can use them to show photos or movies for example.

- Bar chart API documentation