What is a calculated line?

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.

Note

Calculated lines do not automatically update when you change the coordinates. You must add a new calculated line with the updated coordinates.

Examples of calculated lines

Target sales

This time series plot displays actual sales data (the line that connects the symbols) with a calculated line that represents target sales (the straight line). This graph shows that usually actual sales surpassed target sales. However, you might want to examine the instances where sales did not meet the target to determine the cause.

Theoretical distribution of failure times

This graph shows that the actual engine failure times (the histogram) aren't a very good fit with the theoretical distribution (the solid line).

Add a calculated line to a graph

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).

C1 C2 C3 C4
Weight Height X Y
3.97 3.46 1 2
2.5 1.01 5 6
4.2 3.73    
2.19 2.02    
... ...    
Example worksheet and graph

Follow these steps to enter coordinates for a calculated line and then add the calculated line to a graph.

  1. To enter the coordinates for a calculated line:
    1. Name one empty column X and one empty column Y.
    2. In the X column, enter the X coordinates.
      For example, enter 1 and 5.
    3. In the Y column, enter the Y coordinates.
      For example, enter 2 and 6.
  2. Create the scatterplot.
  3. Right-click the scatterplot and choose Add > Calculated Line.
  4. In Y column, enter Y.
  5. In X column, enter X.
  6. Click OK.
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