Frequency polygons show the same information as bar charts, with points joined by lines instead of with vertical bars. Suppose we need to draw a frequency polygon for the data in the table below which contains information about the weights of some ambitious slimmers.
Weight,in kg 
Frequency 
12 

35 

76 

80 

41 

17 
The frequency polygon is:
Notice that the points are plotted as (midpoint of weight interval, frequency).