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leasqr problem - covp is 'NA'!!!
From: |
neo7891 |
Subject: |
leasqr problem - covp is 'NA'!!! |
Date: |
Fri, 15 Apr 2011 09:09:50 -0700 (PDT) |
hey guys,
I'm try to solve exponential fitting with leasqr.
The fitting itself is really good - and I want to measure the estimation
error of parameters.
I found I can get the errors by :
========================================
sqrt(diag(covp))
========================================
but the problem is... my 'covp' is only...
========================================
covp =
NA NA NA NA
NA NA NA NA
NA NA NA NA
NA NA NA NA
========================================
here is the source... I hope I can get help from you!!!! Thanks a
lot!!!!!!!!
========================================
data = load("data2.txt");
x = data(1:length(data),1);
y = data(1:length(data),2);
orgFx = @(x, p) p(1) + p(2) * ( 1 - exp( -p(3) * ( x - p(4))));
pin = ones(1,4);
pin(1) = median(y(1:5));
pin(2) = max(y) - min(y);
pin(3) = abs(log(max(y) - min(y))) / (max(x)-min(x));
pin(4) = min(x);
F = orgFx;
[f,p,kvg,iter,corp,covp,covr,stdresid,Z,r2] = leasqr(x,y,pin,F);
plot(x, y, "r+", x, f, "b-");
fprintf("%f %f %f %f\n", p(1), p(2), p(3), p(4));
========================================
--
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- leasqr problem - covp is 'NA'!!!,
neo7891 <=