Re: [Numpy-discussion] Inversion of near singular matrices.

2011-01-30 Thread Algis Kabaila
> > And if you are trying to solve a least-squares, I think that > you should be using a ridge (or Tikhonov) regularisation: > http://en.wikipedia.org/wiki/Tikhonov_regularization > read in particular the paragraph above the table of content: > you are most likely interested in Gamma = alpha ident

Re: [Numpy-discussion] numpy.linalg.svd documentation

2011-01-30 Thread Charles R Harris
On Sun, Jan 30, 2011 at 10:35 AM, Sturla Molden wrote: > Den 30.01.2011 17:04, skrev Charles R Harris: > > > The v.H is the old, incorrect, version of the documentation. The current > documentation is correct. > > > !!! > > Was it just the documentation that was false, or did SVD return v.H befo

Re: [Numpy-discussion] numpy.linalg.svd documentation

2011-01-30 Thread Pauli Virtanen
On Sun, 30 Jan 2011 18:35:56 +0100, Sturla Molden wrote: > Den 30.01.2011 17:04, skrev Charles R Harris: >> The v.H is the old, incorrect, version of the documentation. The >> current documentation is correct. > > !!! > > Was it just the documentation that was false, or did SVD return v.H > befor

Re: [Numpy-discussion] Help in speeding up accumulation in a matrix

2011-01-30 Thread Nicolas SCHEFFER
Hi all, Thanks for all of the answers, it gives me a lot of new ideas and new functions I didn't know of. @Charles: The reshape way is a great idea! It gives a great alternative to the for loop for your code to be vectorized. I tested it I get %timeit scale_and_add_reshape(R,w,Msr) 1 loops, best o

Re: [Numpy-discussion] create a numpy array of images

2011-01-30 Thread Friedrich Romstedt
2011/1/28 Christopher Barker : > On 1/28/11 7:01 AM, Asmi Shah wrote: >> I am using python for a while now and I have a requirement of creating a >> numpy array of microscopic tiff images ( this data is 3d, meaning there are >> 100 z slices of 512 X 512 pixels.) How can I create an array of images?

Re: [Numpy-discussion] numpy.linalg.svd documentation

2011-01-30 Thread Sturla Molden
Den 30.01.2011 17:04, skrev Charles R Harris: The v.H is the old, incorrect, version of the documentation. The current documentation is correct. !!! Was it just the documentation that was false, or did SVD return v.H before? Sturla ___ NumPy-Discu

Re: [Numpy-discussion] Inversion of near singular matrices.

2011-01-30 Thread Gael Varoquaux
On Sun, Jan 30, 2011 at 04:15:34PM +0100, Sturla Molden wrote: > Den 30.01.2011 07:28, skrev Algis Kabaila: > > Why not simply numply.linalg.cond? This gives the condition > > number directly (and presumably performs the inspection of > > sv's). Or do you think that sv's give more useful informatio

Re: [Numpy-discussion] Help in speeding up accumulation in a matrix

2011-01-30 Thread Gregor Thalhammer
Am 29.1.2011 um 22:01 schrieb Nicolas SCHEFFER: > Hi all, > > First email to the list for me, I just want to say how grateful I am > to have python+numpy+ipython etc... for my day to day needs. Great > combination of software. > > Anyway, I've been having this bottleneck in one my algorithms th

Re: [Numpy-discussion] numpy.linalg.svd documentation

2011-01-30 Thread Charles R Harris
On Sun, Jan 30, 2011 at 8:25 AM, Sturla Molden wrote: > Den 30.01.2011 02:58, skrev Jason Grout: > > Factors the matrix a as u * S * v, > > It actually returns the Hermitian of v, as almost any use of SVD will > require v.H. And by the way, the documentation does not say that the > factorization

Re: [Numpy-discussion] Inversion of near singular matrices.

2011-01-30 Thread Bruce Southey
On Sun, Jan 30, 2011 at 9:15 AM, Sturla Molden wrote: > Den 30.01.2011 07:28, skrev Algis Kabaila: >> Why not simply numply.linalg.cond? This gives the condition >> number directly (and presumably performs the inspection of >> sv's). Or do you think that sv's give more useful information? > > You

Re: [Numpy-discussion] numpy.linalg.svd documentation

2011-01-30 Thread Sturla Molden
Den 30.01.2011 02:58, skrev Jason Grout: > Factors the matrix a as u * S * v, It actually returns the Hermitian of v, as almost any use of SVD will require v.H. And by the way, the documentation does not say that the factorization is u * S * v, but u * np.diag(s) * v.H. Sturla _

Re: [Numpy-discussion] Inversion of near singular matrices.

2011-01-30 Thread Sturla Molden
Den 30.01.2011 07:28, skrev Algis Kabaila: > Why not simply numply.linalg.cond? This gives the condition > number directly (and presumably performs the inspection of > sv's). Or do you think that sv's give more useful information? You can use the singular value decomposition to invert the matrix,

[Numpy-discussion] [ANN] FEMTEC: Trac on open source scientific software

2011-01-30 Thread Gael Varoquaux
Hi list, This is just a note that an extra track at FEMTEC, a conference for computational methods in engineering and science, is open for open source scientific software. The organisers have a taste for Python, so if you want to submit a paper on numerical methods with Python, this is an excellen