Fit Command — Function Library

The Fit command has an ‘Arbitrary Fit’ option. This option allows you to specify the form of the function y = f(x) that you want to solve. For detailed documentation see Fit command > Arbitrary Fit.

This article shows you how to save a to a simple function library, so you don’t have to enter from scratch every time.

Add Function

Consider this example where a points are being fit to normal distribution function.

where σ is the standard deviation and μ is the mean. This is not a standard function under the Fit function menu, so select ‘Arbitrary.’ The function can be entered as the following expression:

1 / (σ * sqrt( 2π )) * exp ( -0.5 (( x - μ ) / σ )^2 )

To add the function library:

  1. Enter the function in the Function form entry box.
  2. Click the gear menu to the right of the entry box.
  3. Select Add function to library.

Now when you create a new Fit command, the expression for this function will be listed when you click the same gear menu.

Remove Function

To remove a function that you entered, that function has to be the current function in the Function form entry box. Click the gear menu, and you will now see the option to ‘Remove from function library .’

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