[Homer-users] Saving Data to Clipboard

[Margaret Duff]

hi ted,  the reason i asked this question is that i am trying to save my
data to use in excel.  i had originally used 0-30s, but when importing
that to excel, it fills a row.  the row isn't long enough, runs out of
columns and clips the file.  do you know of a better way to save the data
or convert it so that i can see my whole data set?  is there any way to
save the data to the clipboard as a column instead of a row?  oh, and i
was using delta optical density, not concentration. sorry for that
confusion.   thanks, margaret


On Mon, 14 Feb 2005, thuppert wrote:

> There are two reasons where this might occur (that I thought of off-hand).
> I don't know if either applies.
>
> 1) By default, the averaging (or deconvolution) preforms a detrend on the
> HRF.  This means that it removes linear trends from the data.  After
> detrending, the change at the zero-point (time=0) is set to zero (this
> removes any DC component).  If the 20-30s component is signifantly different
> from zero mean, then this detrend can produce such results.  Ideally, the
> HRF should return to baseline by the end of the post-stim time (and so no
> problems should occur).  If not, maybe a longer post-time is required.
>
> 2) If you are doing a deconvolution, (particularly if any of the inter-stim
> intervals are less then 30s) then this difference could be the result of the
> 20sec post-time not being long enough to fully model out the tail of the
> HRF.  In that case, the longer post-time is giving a more accurate
> deconvolution.  However, even if the HRF ends by 20s, still a 30s and 20s
> deconvolution can differ depending on the efficancy of the stimulus
> presentation (something set in the orignal experimental design).  The HRF
> window (i.e. pre and post-stimulus times) are actually parameters that would
> go into creating an ideal stimulus presentation for deconvolution.  At the
> very least, think that a 30s deconvolution is fitting the same amount of
> measurements with more unknowns (and hence affects the SNR).
>
>
> *As a side note, I don't think that delta-conc. changes should really ever
> be in the the range of 0.001.  That's a ~1mM change... plus/minus partial
> volume etc. (which is like a 1000% change!!).
>
>
> Ted Huppert, M.Sc.
>
> PhD student-Harvard Univ.
> Dept of Biophysics
> Photon Migration Imaging lab
> Mass General Hospital/CNY
>
> Tele: (617)726-1223
> Cell: (617) 869-1205
>
> thuppert at nmr.mgh.harvard.edu
>
>
>
> -----Original Message-----
> From: homer-users-bounces at nmr.mgh.harvard.edu
> [mailto:homer-users-bounces at nmr.mgh.harvard.edu]On Behalf Of Margaret
> Duff
> Sent: Monday, February 14, 2005 2:35 PM
> To: homer-users at nmr.mgh.harvard.edu
> Subject: [Homer-users] Saving Data to Clipboard
>
>
> Hello,  I am saving on of my channel's data to the clipboard to be looked
> at using Excel.  However, when I save data averaged over -5 to 20 seconds
> and -5 to 30 seconds, the data changes.  I would expect the all the time
> points from the -5 to 20 seconds average to remain in the -5 to 30 seconds
> average data.  They are close but off by about .001 or so, which is kind
> of a lot when looking at delta concentrations.  Is there anything inherent
> to the averaging process or saving data to the clipboard that could cause
> this discrepancy?  Thanks, Margaret Duff
>
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