## quantreg(x,y,tau,or​der,Nboot)

Version 1.3.0.0 (3.94 KB) by
Quantile regression with bootstrapping confidence intervals

Updated 16 Mar 2015

Quantile Regression

USAGE: [p,stats]=quantreg(x,y,tau[,order,nboot]);

INPUTS:
x,y: data that is fitted. (x and y should be columns)
Note: that if x is a matrix with several columns then multiple
linear regression is used and the "order" argument is not used.
tau: quantile used in regression.
order: polynomial order. (default=1)
nboot: number of bootstrap surrogates used in statistical inference.(default=200)

stats is a structure with the following fields:
.pse: standard error on p. (not independent)
.pboot: the bootstrapped polynomial coefficients.
.yfitci: 95% confidence interval on polyval(p,x)

Note: uses bootstrap on residuals for statistical inference. (see help bootstrp)
check also: http://www.econ.uiuc.edu/~roger/research/intro/rq.pdf

EXAMPLE:
x=(1:1000)';
y=randn(size(x)).*(1+x/300)+(x/300).^2;
[p,stats]=quantreg(x,y,.9,2);
plot(x,y,x,polyval(p,x),x,stats.yfitci,'k:')
legend('data','2nd order 90th percentile fit','95% confidence interval','location','best')

For references on the method check e.g. and refs therein:
http://www.econ.uiuc.edu/~roger/research/rq/QRJEP.pdf

### Cite As

Aslak Grinsted (2023). quantreg(x,y,tau,order,Nboot) (https://www.mathworks.com/matlabcentral/fileexchange/32115-quantreg-x-y-tau-order-nboot), MATLAB Central File Exchange. Retrieved .

##### MATLAB Release Compatibility
Created with R14
Compatible with any release
##### Platform Compatibility
Windows macOS Linux

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Version Published Release Notes
1.3.0.0

implemented suggested change from Simeon Yurek in a FEX comment

1.2.0.0

Fixed another small bug.

1.1.0.0

Fixed a few issues with input parameter parsing.

1.0.0.0