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Pedrodala
4 Posts |
 Posted - 12/14/2011 : 02:53:48 AM
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Origin Ver. 8.
Operating System: XP 32-bit
Good day all, I am wondering about removing the background from my Raman data. I have the raman data that has a high slope with undulating curve. I want to get at the undulations by removing the background slope so that the resulting data will retain the peaks but have a linear background.
So, the background on the data now is sloped, I want to fit a slope and remove the intensity from this data. I hope that makes sense.
Does anyone have any knowledge of how to go about this with origin?
Thanks
- pedro - |
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Hideo Fujii
USA
1582 Posts |
Posted - 12/14/2011 : 11:17:13 AM
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Hi pedro,
Maybe you can try "Subtract Baseline" feature in Peak Analyzer ("Analysis: Peaks and Baseline: Peak Analyzer" menu)? In this tool, you can specify the anchor points (in Baseline Mode page), and if your Origin is a Pro version, you can additionally fit anchor points with a function like line, polynomial, exponential, etc., in Create baseline page); then subtract the baseline from your data (in Subtract Baseline page). (If your Origin is non-Pro, you can only interpolates anchors.)
--Hideo Fujii
OriginLab
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Pedrodala
4 Posts |
Posted - 12/18/2011 : 01:44:34 AM
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Thank-you Fujii-san,
I got that to work, but now, any reccomendations on how to systematically pick the baseline/background to be removed?
I am looking at glasses so, the spectra are "wavy" and I've picked a few of the lowest points and then tried to make the whole baseline linear across the entire range of the spectra. That seems to work fine.
So, if this method of choosing a baseline is good then when I calculate the area-under-a-curve do I calculate it to this baseline or to a linear interpolation between to local minima on either side of a peak?
Thanks again,
Pedro
- pedro - |
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Hideo Fujii
USA
1582 Posts |
Posted - 12/19/2011 : 11:23:34 AM
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Hi Pedro,
Not sure what you meant by saying "systematically pick the baseline/background to be removed"; but if your baseline is the same for other data to be fit, you can choose "Use Existing Dataset" in the Baseline Mode page of Peak Analyzer so that you can subtract the previously obtained baseline dataset every time.
--Hideo Fujii
OriginLab |
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Pedrodala
4 Posts |
Posted - 12/21/2011 : 01:01:38 AM
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Hi Fujii,
I have Origin Pro 8.
Okay, I've figured out how to create a baseline from using user defined points through the blpwiz. It was fine.
Now I've moved to a new data set and it won't allow me to create and subtract a baseline. The statement "The Input data are not monotonic increase!" I don't know what this means (from the program's point of view?). The data may not be monotonic however I still which to remove a linear (though sloped) background line but I am unable to create one now?
I have also tried to create a baseline and then use that as the imput baseline to be removed but I can figure out how to go about it that way either?
Thanks,
Pedro
- pedro - |
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Hideo Fujii
USA
1582 Posts |
Posted - 12/22/2011 : 10:27:12 AM
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Hi Pedro,
> it won't allow me to create and subtract a baseline. The statement "The Input data are not monotonic increase!"
It means the XY datasets for the baseline must be sorted in ascending order of X. So, before running Peak Analyzer, you need to sort the worksheet by the values of X dataset. (Choose "Worksheet: Sort Worksheet: Custom" menu, and specify the X column as the sort key.)
Hope this works.
--Hideo Fujii
OriginLab |
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Pedrodala
4 Posts |
Posted - 01/13/2012 : 10:17:31 AM
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Hi Hideo,
okay, now I've got a new issue. After I remove the background the data in the "plot details" window shows that I have 4 things:
1 - "sheetXY... X vs Y" = the original data
2 & 3 - "[Book1]baseline..." files = the 2 background files??
4 - "[book1]subtracted..." = the subtracted values??
And usually there are peaks that the program has picked. I usually delete these since they don't apply to my data.
So, my question is, can I now extract the X-Y values from the background removed data? I don't see how I can use this data except as is and I want to separate it from the old (un-background removed) data.
After this I want to plot it in a stacked line plot to compare edge shifts and such but I need the data set without the background. How is this done?
Thanks,
Pedro
- pedro - |
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Removing flourescent background