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Using Formula Entry, it is possible to subtract the values of one curve from another curve. This can be done if the curves share the same X values or if they were plotted using two different sets of X values.

If the curves use the same set of X values: You can use Formula Entry to subtract the values of one Y column from another Y column to find the difference between the two. If your Y1 data is in c1, and your Y2 data is in c2, you can use the formula c3=c2-c1 to find the difference and store the results in c3.

If the curves use separate sets of X values: KaleidaGraph provides a table() command in Formula Entry that can be used to perform linear interpolation. Using this command, you can find the Y values of a curve at specific X locations. This would let you find the Y values for one of your curves at the X values used by the other curve.

  • As an example, suppose you have a data set containing the following: c0 is the X1 data, c1 is the Y1 data, c2 is the X2 data, c3 is the Y2 data
  • If you run the following command in Formula Entry, c4=table(c0,c2,c3), c4 will contain the values from the Y2 curve at the X1 values. You can then run the formula c5=c4-c1 to find the difference between the two curves.


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Posted in: Formula Entry: General Questions, Plots & Plot Windows