Version 1.34.0.0 (2.34 KB) by
A convenience function to superimpose a polynomial fit to already plotted data

Updated Wed, 27 Jul 2022 13:32:07 +0000

** What is it?
This convenience function allows you to quickly add a fit line to data after they have been plotted. e.g.
>> plot(myData)
Add fit line returns the fit parameters and handles to the plot objects.
** Details
The stats toolbox is required for the 'linear' and 'quadratic' options only.
Purpose
Add one or more fit lines to some or all data in axes "ax" or,
without ax specified, to the current axes.
Inputs
*poolFits [optional 0 by default] -
if 1 we fit a single line to all data series on the current
axes.
*modelType ['linear' by default] - If 'linear' it fits a straight line
using the regress function from the stats toolbox. If 'quadratic' it
fits a second-order polynomial using regress. The output from regress is
returned. If modelType is an integer, the function fit a polynomial of
this order using polyfit, which is not part of the stats toolbox. The
output of polyfit is then returned.
*lineprops [optional 'b-' by default]
*ax [optional - gca by default]
Outputs
out - the fit parameters and plot handles
Examples
clf
%Fit two seperate lines
subplot(1,3,1), hold on, x=-5:0.1:5;
y=1+1*x+randn(size(x))*2; plot(x,y,'.k')
y=2-4*x+randn(size(x))*2; plot(x,y,'.r')
%Fit one line to two sets of data
subplot(1,3,2), hold on
x=-5:0.2:0; y=0.3*x+randn(size(x))*2; plot(x,y,'.k')
x=0:0.2:5; y=0.3*x+randn(size(x))*2; plot(x,y,'.r')
subplot(1,3,3)
x=-5:0.1:5;
y=2+0.3*x+0.5*x.^2+randn(size(x))*2;
plot(x,y,'.k')
OR:
Rob Campbell - December 2009

### Cite As

##### MATLAB Release Compatibility
Created with R2022a
Compatible with R2011b to R2022a
##### Platform Compatibility
Windows macOS Linux
##### Categories
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Version Published Release Notes
1.34.0.0

Polynomial fit plot now produces a line that is the same color as the data points.

1.33.0.0

Fix bug in polyfit section: x data were being sorted but not y data.
Tidy code.

1.31.0.0

clarify what this function does

1.3.0.0

Correct indexing bug

1.2.0.0

the polynomial fit was not return plot handles

1.1.0.0

Improved error checking: removes text and patch elements before acquiring plot data.
Added ability to fit higher order polynomials using polyfit and polyval.

1.0.0.0