3.30 FAQ-258 How can I carry out curve fitting with X error?

NLFit-X-Err

Last Update: 7/19/2018

Linear Fit

You can perform linear fitting with X error bars; use the Analysis: Fitting: Fit Linear with X Error menu item.

Nonlinear Curve Fitting

To perform nonlinear curve fitting with error data, use the orthogonal distance regression (ODR) algorithm:

Highlight the dataset/data plot you would like to fit.
Select Analysis: Fitting: Nonlinear Curve Fit to open the NLFit dialog.
Select a fitting function and choose Orthogonal Distance Regression as the Iteration Algorithm. In the Data Selection section of the Settings tab, specify weighting (error), as needed, for X and Y.

If your error data are in columns (designated as X Error/Y Error), you would generally choose Instrumental as your weighting method and identify the error bar column(s). If the error data are in columns designated as something other than error, you can choose Arbitrary as your weighting method.

Nonlinear Implicit Curve Fitting

For implicit fitting functions, select Analysis: Fitting: Nonlinear Implicit Curve Fit to open the NLFit dialog, and specify the weight (error) in the same way.