Select exactly two Y columns.
Select required data.
Select Plot > Statistical: Population Pyramid.
This graph type is also known as Tornado Plot, Tornado Diagram, Tornado Chart or Butterfly Chart. It is a type of bar chart where two sets of data series are displayed side by side, and gives a quick glance of the difference between two groups with same parameters. See the example as below:
The sample graph at top of this page presents the population pyramid about males and females at a certain year. You can compare the female and male at any age range in this year easily. To plot such a graph, you have to start from two data columns contain the population numbers of the male and female respectively, and these two columns will be plotted as two bar charts into two layers(left and right). The vertical axis shows the age groups which are always age ranges, such as 5-9 years; the horizontal axis shows the population of each age range.