A calculated line identifies a target or theoretical relationship between variables on the x- and y-axes. You can compare your actual graphed values against this line as you would any other reference line. But, whereas standard reference lines are a straight line at a single value on one scale only, calculated lines can be curves, sloped lines, or complex polylines. Similarly, while you can add a standard reference line by designating a single value on one axis, producing a calculated line requires two columns of values that are used as y- and x-coordinates. The calculated line is plotted along these coordinates. These coordinates may be derived from a function or some other formula.
Calculated lines do not automatically update when you change the coordinates. You must add a new calculated line with the updated coordinates.
For example, you create a scatterplot and you want to add a line drawn with specific coordinates. The calculated line coordinates are (1,2) and (5,6).
Follow these steps to enter coordinates for a calculated line and then add the calculated line to a graph.