[SciPy-user] lstsq

Bruce Southey bsouthey@gmail....
Thu May 8 09:39:52 CDT 2008


Gregor Hagelueken wrote:
> Hi,
>
> I would like to use lstsq to fit a curve y using a simple linear 
> combination of three spectra (spectrum1-3 see below). Since the 
> program below always crashes, I played around with it and found that 
> it does not crash if I copy the contents of the array "spectrum2" to 
> the array "spectrum3" (using spectrum3[0:36]=spectrum2[0:36]). But as 
> soon as I change one of the numbers in array "spectrum3" it crashes again.
>
> What is the mistake?
>
> Thanks,
> Gregor
>
> from numpy import *
> from numpy.random import normal
> from pylab import *
>
> t = arange(205, 241, 1.0)
>
> #spectrum1
> spectrum1=array([-25.35,-30.85,-34.6,-36.5,-36.75,-35.95,-35.2,-34.2,-33.6,-33.55,-33.8,-34.2,-34.2,-34.8,-35.4,-36.25,-36.6,-36.85,-36.55,-35.85,-35.05,-33.55,-31.7,-29.6,-27.15,-24.1,-21.5,-18.95,-16.4,-13.85,-11.45,-9.43,-7.76,-6.24,-4.81,-3.88])
> #spectrum2
> spectrum2=array([8.08,5.37,1.24,-3.07,-6.02,-8.84,-11.2,-13.05,-14.85,-17.75,-17.5,-18,-18.35,-18.65,-18.15,-17.45,-17.15,-16.3,-15,-13.15,-11.57,-9.76,-7.98,-5.79,-3.73,-2.37,-0.61,0.08,0.15,1.17,0.73,0.77,0.38,0.56,0.28,0.64])
> #spectrum3
> spectrum3=array([-25.8,-21.45,-18.0,-15.59,-12.82,-10.41,-8.41,-6.58,-4.99,-3.85,-2.62,-1.74,-1.02,-0.5,-0.13,0.17,0.03,-0.08,-0.32,-0.35,-0.48,-0.75,-1.12,-1.31,-1.5,-1.55,-1.17,-1.04,-0.72,-0.46,-0.14,0.21,0.01,0.23,0.03,-0.22])
>
> #make curve y
> y=0.8*spectrum1+0.1*spectrum2+0.2*spectrum3+ normal(0.0, 1.0, len(t))
>
> from numpy.linalg import lstsq
> Nparam = 3
> A=zeros((len(t), Nparam),float)
>
> #helix
> A[:,0]=spectrum1
> #beta
> A[:,1]=spectrum2
> #coil
> A[:,2]=spectrum3
>
> (p, residuals, rank, s) = lstsq(A,y)
>
> #A=p*A
> #fit = A[:,0]+A[:,1]#+A[:,2]
> #plot (t, y)
> #plot (t, fit)
> ------------------------------------------------------------------------
>
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>   
Hi,
This works for me on Linux x86_64, Python 2.5 and '1.1.0.dev5133'.
What are you using and what is the actual error message?

Bruce


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