# Documentation

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# sftool

Open Curve Fitting app

## Syntax

`sftoolsftool(x,y,z)sftool(x,y,z,w)sftool(filename)`

## Description

 Note:   `sftool` will be removed in a future release. Use `cftool` instead. See Curve Fitting.

`sftool` opens Curve Fitting app or brings focus to the tool if it is already open.

`sftool(x,y,z)` creates a fit to `x` and `y` inputs (or predictor data) and `z` output (or response data). `sftool` opens Curve Fitting app if necessary.

`x`, `y`, and `z` must be numeric, have two or more elements, and have compatible sizes. Sizes are compatible if either:

• `x`, `y`, and `z `all have the same number of elements, or

• `x` and `y` are vectors, `z` is a 2D matrix, where ```length(x) = n```, `length(y) = m`, and ```[m,n] = size(z)```.

`sftool(x,y,z,w)` creates a fit with weights `w`. `w` must be numeric and have the same number of elements as `z`.

`sftool(filename)` loads the surface fitting session in `filename` into Curve Fitting app. The `filename` should have the extension `.sfit`.

`Inf`s, `NaN`s, and imaginary parts of complex numbers are ignored in the data.

Curve Fitting app provides a flexible interface where you can interactively fit curves and surfaces to data and view plots. You can:

• Create, plot, and compare multiple fits

• Use linear or nonlinear regression, interpolation, local smoothing regression, or custom equations

• View goodness-of-fit statistics, display confidence intervals and residuals, remove outliers and assess fits with validation data

• Automatically generate code for fitting and plotting surfaces, or export fits to workspace for further analysis