Hi Hamid Muili , what do you want to do exactly? If you are using the quantreg comand, here is a little example.

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')

Thanks @Juan Bueno. What quantile on quantile regression does is that, it measures the effect of various independent variables at different quantile of the independent variables on different quantile of the dependent variable. Unlike the standard quantile regression which only measures the effect of the independent variables at a particular point on different quantiles of the dependent variables