Microsoft KB Archive/68639

{|
 * width="100%"|

Excel: Interpolating Using Goal Seeker

 * }

-

The information in this article applies to:


 * Microsoft Excel for Windows, versions 3.0, 4.0, 5.0

-

SUMMARY
In Microsoft Excel, you can use Goal Seeker to interpolate values between two known values. This can be used, for example, for creating an XYZ graph where many X and Y values need to be plotted, and constraints are known for X and Y. Interpolating means to insert a specified number of values between two known values.

MORE INFORMATION
For example, suppose you want to interpolate 48 values between the numbers -3 and 3, for a total of 50 values. The goal is to calculate 48 values, all of which differ by a constant. To use Goal Seeker, you need to have an empty cell to hold this unknown constant. To accomplish this do the following:


 * 1) Enter the value -3 into cell A2. Cell A1 is empty and will be the cell for the unknown constant.
 * 2) In cell A3, enter the formula =A2+$A$1 (noting the absolute and relative referencing).
 * 3) Highlight cells A3:A51. Choose Fill Down from the Edit menu to fill this formula down to cell A51. All cells will have a -3 entered because A1 is blank.
 * 4) From the Tools menu (Formula menu in versions 3.0 and 4.0), choose Goal Seek.
 * 5) In the Set Cell box, enter A51.
 * 6) In the To Value box, enter 3 (the final goal).
 * 7) In the By Changing Cell box, enter A1 (the constant).
 * 8) Choose OK and Goal Seeker will interpolate all values between -3 and +3.