SRS1 Cubic Spline for Excel - Using the Cubic Spline Functions in Excel
How to Use the Cubic Spline Functions in Excel - This will demonstrate how to use the functions in SRS1 Cubic Spline for Excel.
(1) Make sure that SRS1 for Cubic Spline for Excel is installed and enabled. You can tell if it is installed if the "SRS1 Splines" ribbon tab is present in Excel.
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(2) Select the cell where you want the cubic spline function to be placed, and then click the small Excel "Insert Function" button on the equation editor (labelled "fx"). In the Insert Function dialog that appears, select the 'SRS1Splines.Functions25' function group.
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(3) All available custom functions from SRS1 Cubic Spline for Excel will be listed. Select the function that you would like to use, and then click the 'OK' button.
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(4) Enter ranges for the Source_Data_X, Source_Data_Y, and input_x values. Then click the 'OK' button.
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At this point, your function should be set, and you should see the result in the cell.
A Few Important Notes
  • Absolute references - Notice that the source X and Y ranges use absolute references (uses "$"). This is probably needed if you are going to be copying the function down a column and want to always be using the same source data.
  • Array Output - If you want to calculate the spline values for many values, all based on the same source data set, then you can make the cubic spline solve faster by using an array formula. To do this, instead of setting "input_x" to a single value, you set it to a array of values. For an explanation and demo showing how to make this work, see our video demo on array formulas on the 'Data Curve Fit Creator' product page.