# 15.3.4.3 Defining Derived Parameters

Derived parameters are additional parameters computed using the fitted parameter values. You can define your own derived parameters for any built-in or user-defined fitting functions.

For example, the built-in Gauss function fits the peak area with the following equation:

$y=y_0+\frac A{w\sqrt{\pi/2}}e^{-2\frac{(x-x_c)^2}{w^2}}$

Suppose that you also want to know the peak height, which can be computated as follows:

$h=\frac A{w\sqrt{\pi/2}}$

## How to Define Derived Parameters

You need first to go to the Variables and Parameters page of Fitting Function Builder and input the name of the derived parameters in Derived Parameters edit box. Then input the expressions of the derived parameters in the Derived Parameters page.

Or, you can open Fitting Function Organizer to define derived parameters directly in the Derived Parameters box.

After fitting, Origin will compute the height and include the result in the Parameters table on the fitting results worksheet.

Note:

1. If you need to define multiple derived parameters, please define them in separate lines.
2. Derived parameters cannot be computed from other derived parameters.
3. Origin will output the standard error of all derived parameters by default, just as other parameters.