[SciPy-user] lstsq

[Nils Wagner]

On Thu, 08 May 2008 16:06:10 +0100
  Gregor Hagelueken <gh50 at st-andrews.ac.uk> wrote:
> Bruce Southey wrote:
>> 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)
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> SciPy-user mailing list
>>> SciPy-user at scipy.org
>>> http://projects.scipy.org/mailman/listinfo/scipy-user
>>>   
>>>     
>> 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
>> _______________________________________________
>> SciPy-user mailing list
>> SciPy-user at scipy.org
>> http://projects.scipy.org/mailman/listinfo/scipy-user
>>   
> Hi Bruce,
> 
> I have a Vista PC (Intel Core2Duo) and Python 2.5 
>installed.
> 
> I do not get any error message, it just hangs up, uses 
>50% of CPU and does not stop again.
> 
> Sorry, but I am not sure what you mean by 
>'1.1.0.dev5133'?

Python 2.5 (r25:51908, Jan 10 2008, 18:01:52)
[GCC 4.1.2 20061115 (prerelease) (SUSE Linux)] on linux2
Type "help", "copyright", "credits" or "license" for more 
information.
>>> import numpy
>>> numpy.__version__
'1.2.0.dev5148'
>>>

Nils


> 
> Thanks,
> Gregor