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Combining Graphs Arithmetically

IGB allows you to work with numerical/graph data, allowing you to do quantitative comparisons between data sets. This is especially useful for comparing experimental results between a control and treatment group, for instance. You may need to compare the relative differences in expression levels between two graphs that represent data that occupy the identical genomic position on the chromosome, or you may need to generate an average.  For example, a graph of cancerous cells will show what's turned on or off when compared to a graph of normal cells.  Results that show significantly more or less activity than a control graph for the same region may indicate an area of interest.

Arithmetically combining two graphs may make the differences and correlations easier to see. 

To arithmetically combine two graphs:

• Shift-click the bar at the left end of each graph to select the graph.  The graph you click first is A, the graph you click second is B.
• Use one of the four Combine buttons in the Advanced portion of the Graph Adjuster tab labeled A+B, A-B, A*B, and A/B.
• Alternatively, right-click the bar at the left end of either graph and choose Combine Graphs, then choose one of the following:
  • Create Sum Graph (A+B) 
  • Create Difference Graph (A-B)
  • Create Product Graph (A*B)
  • Create Ratio Graph (A/B)

Image RemovedWhile you can use the Combine Annotations functions to qualitatively locate regions of interest, combining graphs will give you quantitative answers.

IGB allows you to work with 2 graph tracks at a time. The first track selected will be given a temporary label of 'A'. Shift click selection of the second track will give it the temporary label 'B'. After the two tracks have been selected, you choose the mathematical function from the four buttons: Image Added

IGB will open an new track for the newly created graph. It will be titled as the name of the function performed, and then each of the original tracks in parenthesis. The new track can be adjusted for style and display just as any other graph track. Note: IGB will not display negative or fractional numbers, only positive integers. Keep this in mind when you designate which graph tracks will be 'A' and 'B'.