Home / Com Products / Product Guide / Choosing a Graph

Line graph

Line graphs show trends in values, usually over time.

• In a line graph, the X axis usually represents an independent variable, which is most often a time scale. The Y axis usually shows a dependent variable, such as a quantity or percentage.
  
  
• Line graphs can chart multiple data sets, each represented by a single line or symbol sequence, with as many data points as are meaningful.
  
  
• If you don’t supply X positions for data points, Graphics Server places them at increments of 1, starting at 0.
  
  
• In drawing a line graph, you can use any combination of lines, symbols, and vertical "sticks". See the example above and the ones on the next page.
  
  
• The line graph is also available in a 3D version called the tape graph.
  
  
• You can create special graphing effects by drawing a line graph on top of a another graph (bar, area, scatter, high-low-close, or another line graph). These "overlay" line graphs are always drawn on the same X scale as the first ("primary") graph, and you can either use the same Y scale for both graphs or add a second Y axis.
  
  

Use a line graph...

• To show the trend of one or more data sets over time or another continuous scale.
  
  
• With lines to suggest a gradual flow between data points.
  
  
• With symbols to clarify the position of individual data points.
  
  
• With symbols alone (no lines) to downplay an impression of flow between data points.
  
  
• With vertical sticks to reinforce the grid and to highlight the value of data points.
  

Other graph types to consider

• If your main focus is on the quantities at various data points rather than the trends in those quantities, consider an absolute area graph .

Along with (or instead of) lines, you can draw symbols at the position of data points.		Another styling option is vertical sticks, which are drawn between data points and the X axis.

• If you're graphing discrete values--with data points that are based on two independent variables and don’t necessarily occur at regular intervals--use a scatter graph.
  
  
• If your data points aren’t consecutive--for example, if you want to graph data only for 1987, 1990, and 1992--an absolute area graph may be more appropriate.
  
  
• If you’re graphing data expressed as angles, try a polar graph.
  
  

With Graphics Server's "overlay" graphing feature, you can draw a line graph on top of a primary graph (vertical bar, area, scatter, high-low-close or open-high-low-close, candlestick, or another line graph).