FrequencyPolygon Command
Frequency polygon is a line graph drawn by joining all the midpoints of the top of the bars of a histogram. Therefore usage of this command is the same as usage of Histogram Command. 
 FrequencyPolygon( <List of Class Boundaries>, <List of Heights> )

Creates a frequency polygon with vertices in given heights. The class boundaries determine the xcoordinate of each vertex.
FrequencyPolygon({0, 1, 2, 3, 4, 5}, {2, 6, 8, 3, 1})
creates the corresponding line graph.
 FrequencyPolygon( <List of Class Boundaries>, <List of Raw Data>, <Boolean Use Density>, <Density Scale Factor (optional)> )

Creates a frequency polygon using the raw data. The class boundaries determine the xcoordinates of vertices and are used to determine how many data elements lie in each class. The ycoordinate of a vertex is determined as follows

If Use Density = true, height = (Density Scale Factor) * (class frequency) / (class width)

If Use Density = false, height = class frequency

By default, Use Density = true and Density Scale Factor = 1.
 FrequencyPolygon( <Boolean Cumulative>, <List of Class Boundaries>, <List of Raw Data>, <Boolean Use Density> , <Density Scale Factor (optional)> )

If Cumulative is true this creates a frequency polygon where each vertex ycoordinate equals the frequency of the class plus the sum of all previous frequencies.
For further examples see Histogram Command. 