thanks, steve, that might do the job ... but won't that also include
the variances from the other regressors? or is sigmasqareds the
variance after removing the whole model ( that is , var(Y - X*beta) )
-L
On Jun 23, 2009, at 2:29 PM, Steve Smith wrote:
> Hi - you can just take the residuals (take root of sigmasquareds)
> and divide by sqrt(ntimepoints) to get standard deviation of the
> mean_func - I'm pretty sure that's close enough....?
>
> Cheers.
>
>
> On 23 Jun 2009, at 10:50, Luis Hernandez wrote:
>
>> right ... there is not Beta_hat_0 in FSL - it's just my way of
>> saying estimate of baseline regressor parameter - (the one I'm
>> after). In case you're wondering, I'm trying to use it to estimate
>> spin density.
>>
>> thanks again
>>
>> -L
>>
>>
>> On Jun 23, 2009, at 12:23 PM, Mark Jenkinson wrote:
>>
>>> Hi,
>>>
>>> In FSL there is no pe0 or beta_hat_0 file as we remove
>>> the mean prior to setting up the GLM. Hence there is
>>> no constant (mean) regressor and so no parameter estimate
>>> (or variance) associated with that.
>>>
>>> I'm not sure where you are getting Beta_hat_0 from.
>>>
>>> All the best,
>>> Mark
>>>
>>>
>>> On 23 Jun 2009, at 16:28, Luis Hernandez wrote:
>>>
>>>> thanks, Mark.
>>>>
>>>> Beta_hat_0 is the same as the mean (assuming no pre-whitening),
>>>> but I don't think the variance estimate of Beta_hat_0 the same as
>>>> the variance of the signal. oh, well...
>>>>
>>>>
>>>> -Luis
>>>>
>>>>
>>>>
>>>>
>>>> On Jun 23, 2009, at 10:59 AM, Mark Jenkinson wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> If you are talking about the mean signal as the baseline
>>>>> regressor then
>>>>> I'm afraid the answer is no. We do not remove the mean signal
>>>>> via a
>>>>> regressor, but instead remove it from the signal and the model
>>>>> in the
>>>>> pre-statistical filtering. Hence we do not generate values or
>>>>> variances
>>>>> for it. But it is easy to calculate the mean using fslmaths and
>>>>> -Tmean
>>>>> on the original data if that is all you want.
>>>>>
>>>>> All the best,
>>>>> Mark
>>>>>
>>>>>
>>>>> On 23 Jun 2009, at 15:49, Luis Hernandez wrote:
>>>>>
>>>>>> Dear FSL experts,
>>>>>>
>>>>>> Is there a way to get FSL to dump the parameter estimate for
>>>>>> the baseline regressor into a file, like pe0? (It looks like
>>>>>> the mean_func file might do the trick ... is this right?) BUT
>>>>>> more importantly, how about its variance estimate? can that be
>>>>>> dumped out? FEAT writes out varcope files based on the
>>>>>> specified contrasts but I don't see how to make a contrast that
>>>>>> uses the baseline regressor, since it is kind of "hidden" ?
>>>>>>
>>>>>> I apologize if I missed something obvious. thanks in advance
>>>>>>
>>>>>> -Luis
>>>>>>
>>>>>> --
>>>>>> ( http://www.eecs.umich.edu/~hernan )
>>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> ( http://www.eecs.umich.edu/~hernan )
>>>>
>>>
>>>
>>
>> --
>> ( http://www.eecs.umich.edu/~hernan )
>>
>
>
> ---------------------------------------------------------------------------
> Stephen M. Smith, Professor of Biomedical Engineering
> Associate Director, Oxford University FMRIB Centre
>
> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
> ---------------------------------------------------------------------------
>
>
--
( http://www.eecs.umich.edu/~hernan )
|