[pymvpa] Error with from mvpa2.tutorial_suite import *

2014-01-23 Thread Payal Chakraborty
Hi All, I am trying to get started on the tutorial, but when entered from mvpa2.tutorial_suite import * I got the error message below. Does anyone know why this is happening? In [*8*]: from mvpa2.tutorial_suite import *

Re: [pymvpa] Error with from mvpa2.tutorial_suite import *

2014-01-23 Thread Nick Oosterhof
On Jan 23, 2014, at 6:03 PM, Payal Chakraborty wrote: I am trying to get started on the tutorial, but when entered from mvpa2.tutorial_suite import * I got the error message below. Does anyone know why this is happening? [...] In [8]: from mvpa2.tutorial_suite import *

Re: [pymvpa] Error with from mvpa2.tutorial_suite import *

2014-01-23 Thread Payal Chakraborty
Hi Nick, Thank you very much for your prompt response. I greatly appreciate all of your help. Best, Payal On Thu, Jan 23, 2014 at 12:15 PM, Nick Oosterhof nikolaas.ooster...@unitn.it wrote: On Jan 23, 2014, at 6:03 PM, Payal Chakraborty wrote: I am trying to get started on the tutorial,

[pymvpa] Justification for trial averaging?

2014-01-23 Thread Shane Hoversten
I have a question about trial averaging in MVPA, by which I mean taking the average response of a certain stimulus class, and using this average value as input to the classifier, instead of feeding it the responses from the individual trials themselves. For instance, in the original Haxby

Re: [pymvpa] Justification for trial averaging?

2014-01-23 Thread Brian Murphy
Hi, I'm not sure about the motivation for averaging in that particular paper - if I had to guess, it might be that they chose a simple exposition to present what at that time was a completely novel approach. But averaging can work as a simple but effective method to improve the signal/noise

Re: [pymvpa] Error with from mvpa2.tutorial_suite import *

2014-01-23 Thread Nick Oosterhof
On Jan 23, 2014, at 6:38 PM, Payal Chakraborty wrote: Thank you very much for your prompt response. I greatly appreciate all of your help. You're welcome. It turned out there was some offending code that could be safely removed, so I just did that:

Re: [pymvpa] Justification for trial averaging?

2014-01-23 Thread Francisco Pereira
I agree with every one of Brian's points, and I'll toss one more in. You' want to average if the analysis you want to do is to look at similarity patterns, rather than train classifiers. It might have to be combined with permutation tests (e.g. you average within things labelled as being in the

Re: [pymvpa] Justification for trial averaging?

2014-01-23 Thread Shane Hoversten
Thanks Brian and Francisco. Francisco, you said: You' want to average if the analysis you want to do is to look at similarity patterns, rather than train classifiers. It might have to be combined with permutation tests (e.g. you average within things labelled as being in the same class within

Re: [pymvpa] Justification for trial averaging?

2014-01-23 Thread J.A. Etzel
I also agree, and will toss in a few more ideas: But forming decisions boundaries over features is exactly what a classifier is meant to do, so why not just throw all these different exemplars into the mix, and let the classifier figure out its own notion of prototypicality? I think because of

[pymvpa] PyMVPA Growing Nerual Gas implementation

2014-01-23 Thread Jiang, Zhiguo
Hi, All this might be unrelated to PyMVPA. but I am trying to find a good implementation of clustering using Grown Neural Gas algorithm. I couldn't find any information on PyMVPA. MDP offers growing neural gas class but it is not implemented for fMRI data. anyone has any idea either finding a

Re: [pymvpa] Justification for trial averaging?

2014-01-23 Thread MS Al-Rawi
I think a correlation classifier/method was used in Haxby's et al 2001 work, and it gave high classification accuracy using the averages.  One might argue that, although not sure about this, assigning a volume/exemplar to a single label/condition is problematic, thus, averaging is a good

Re: [pymvpa] Justification for trial averaging?

2014-01-23 Thread MS Al-Rawi
I think a correlation classifier/method was used in Haxby's et al 2001 work, and it gave high classification accuracy using the averages.  One might argue that, although not sure about this, assigning a volume/exemplar to a single label/condition is problematic, thus, averaging is a good