问题
I'm trying to learn myself with data visualization and when I'm going through the bar chart I'm stuck with the following thing.
In the graph there is a vertical black line on each bar in the bar char. What exactly signifies that overlay-ed black line. Thanks for your help
回答1:
This looks like vertical error bars.
Error bars are a graphical representation of the variability of data and are used on graphs to indicate the error, or uncertainty in a reported measurement.
来源：https://stackoverflow.com/questions/35193996/what-is-the-overlay-line-on-each-bar-in-a-bar-chart