addFitLine

A convenience function to superimpose a polynomial fit to already plotted data
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Updated Wed, 27 Jul 2022 13:32:07 +0000

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** 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)
>> out=addFitLine;
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.
function out=addFitLine(poolFits,modelType,lineprops,ax)
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')
H=addFitLine
%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')
H=addFitLine(1)
%Fit one quadratic
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')
addFitLine([],'quadratic')
OR:
addFitLine([],2)
Rob Campbell - December 2009

Cite As

Rob Campbell (2024). addFitLine (https://www.mathworks.com/matlabcentral/fileexchange/26323-addfitline), MATLAB Central File Exchange. Retrieved .

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