# Spline Construction

Create splines including B-form, tensor-product, NURBs, and other
rational splines

Using the Curve Fitter app or the `fit`

function, you can
fit cubic spline interpolants, smoothing splines, and thin-plate
splines. Other Curve Fitting Toolbox™ functions allow more specialized control over spline
construction. For example, you can use the function `csapi`

for cubic spline
interpolation. For more information, see How to Construct Splines.

## Functions

`bspline` | Plot B-spline and its polynomial pieces |

`csape` | Cubic spline interpolation with end conditions |

`csapi` | Cubic spline interpolation |

`csaps` | Cubic smoothing spline |

`cscvn` | “Natural” or periodic interpolating cubic spline curve |

`franke` | Franke's bivariate test function |

`getcurve` | Interactive creation of cubic spline curve |

`ppmak` | Put together spline in ppform |

`rpmak` | Put together rational spline |

`rscvn` | Piecewise biarc Hermite interpolation |

`rsmak` | Put together rational spline for standard geometric shapes |

`spap2` | Least-squares spline approximation |

`spapi` | Spline interpolation |

`spaps` | Smoothing spline |

`spcrv` | Spline curve by uniform subdivision |

`splinetool` | Experiment with some spline approximation methods |

`spmak` | Put together spline in B-form |

`spterms` | Explain spline terms |

`stmak` | Put together function in stform |

`tpaps` | Thin-plate smoothing spline |

`titanium` | Titanium test data |

## Topics

### Introduction to Splines

**Introducing Spline Fitting**

Tools for interactive and programmatic spline fitting in Curve Fitting Toolbox.**Curve Fitting Toolbox Splines and MATLAB Splines**

How Curve Fitting Toolbox extends the splines (or piecewise-polynomial functions) of MATLAB^{®}.**Types of Splines: ppform and B-form**

Learn about the definitions of the ppform and B-form splines.**B-Splines and Smoothing Splines**

Learn about the definitions of the B-form and smoothing splines.**Multivariate and Rational Splines**

Learn how to construct multivariate and rational splines.**The ppform**

Learn about the definition of the ppform spline.**The B-form**

Learn about the definition of B-form splines.

### Fundamental Spline Methods

**Cubic Spline Interpolation**

Use cubic splines to interpolate smooth data, choosing knots and smoothness.**Vector-Valued Functions**

Use vector-valued splines to plot curves through given points.**Fitting Values at N-D Grid with Tensor-Product Splines**

Use vector-valued splines to approximate gridded data in any number of variables using tensor-product splines.**Fitting Values at Scattered 2-D Sites with Thin-Plate Smoothing Splines**

Use the thin-plate smoothing spline for work with scattered bivariate data. Tensor-product splines are good for gridded (bivariate and even multivariate) data.**Constructing and Working with ppform Splines**

Learn how to construct ppform splines.**Constructing and Working with B-form Splines**

Learn how to construct B-form splines.**Multivariate Tensor Product Splines**

Learn how to construct multivariate splines.**Constructing and Working with Rational Splines**

Learn how to construct rational splines.**Constructing and Working with stform Splines**

Learn how to construct stform splines.**Least-Squares Approximation by Natural Cubic Splines**

The construction of a least-squares approximant usually requires that one have in hand a basis for the space from which the data are to be approximated.**Solving A Nonlinear ODE**

This section discusses these aspects of a nonlinear ODE problem:**Construction of the Chebyshev Spline**

This section discusses these aspects of the Chebyshev spline construction:**Approximation by Tensor Product Splines**

Because the toolbox can handle splines with*vector*coefficients, it is easy to implement interpolation or approximation to gridded data by tensor product splines, as the following illustration is meant to show.**How to Construct Splines**

This example shows how to construct splines in various ways using the spline functions in Curve Fitting Toolbox™.**Construct and Work with the B-form**

This example shows how to construct and work with the B-form of a spline in Curve Fitting Toolbox™.**Construct and Work with the PPFORM**

This example shows how to construct and work with the ppform of a spline in Curve Fitting Toolbox™.**How to Choose Knots**

This example shows how to select and optimize knots using the`optknt`

and`newknt`

commands from Curve Fitting Toolbox™.

### Fitting Splines to Data

**Cubic Spline Interpolation**

This example shows how to use the`csapi`

and`csape`

commands from Curve Fitting Toolbox™ to construct cubic spline interpolants.**Cubic Smoothing Splines**

This example shows how to use the`csaps`

and`spaps`

commands from Curve Fitting Toolbox™ to construct cubic smoothing splines.**Fitting a Spline to Titanium Test Data**

This example shows how to use commands from Curve Fitting Toolbox™ to fit a spline to titanium test data with manual and automatic selection of knots.

### Spline Applications

**Splines in the Plane**

This example shows how to use the`spmak`

,`spcrv`

,`cscvn`

and`rscvn`

commands from Curve Fitting Toolbox™ to construct spline curves in the plane.**Constructing Spline Curves in 2D and 3D**

This example shows how to use the`cscvn`

command from Curve Fitting Toolbox™ to construct cubic spline curves in two and three dimensions.**Smoothing a Histogram**

This example shows how to use spline commands from Curve Fitting Toolbox™ to smooth a histogram.**Bivariate Tensor Product Splines**

This example shows how to use the spline commands in Curve Fitting Toolbox™ to fit tensor product splines to bivariate gridded data.**Solving a Nonlinear ODE with a Boundary Layer by Collocation**

This example shows how to use spline commands from Curve Fitting Toolbox™ solve a nonlinear ordinary differential equation (ODE).**Construction of a Chebyshev Spline**

This example shows how to use commands from Curve Fitting Toolbox™ to construct a Chebyshev spline.