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 Spacing of points for Savitzky Golay Smoothing		  New Topic  Reply to Topic
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gpd

Canada
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Posted - 11/30/2006 :  6:30:49 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Version (Select Help-->About Origin): 7.5
Operating System: Windows 2000

I am attempting to smooth & differentiate a UV/Vis spectrum using a Savitzky-Golay filter. My data is equally spaced, however the spacing is not 1 nm. Rather, the spacing between data points is 1.11604 nm. When I attempt to use the Savitzky-Golay filters, I get an error message stating that my points are not equally spaced (even though they are). Is there a way to use the Savitzky-Golay filter on data that has equal but non-unity spacing? Thanks a bunch for any input.

Cheers,

Greg

Mike Buess

USA
3037 Posts
Posted - 11/30/2006 :  7:19:03 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Greg,

The SG filter works fine with noninteger X spacings so check your worksheet for odd (spurious) data points. Perhaps some of your file header leaked through to become the first data point. Or maybe your file has a tailer which was imported by mistake.

Mike Buess
Origin WebRing Member
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gpd

Canada
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Posted - 11/30/2006 :  7:47:17 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Mike,

Thanks for the reply. I went back and checked my file. I was importing the data from an excel spreadsheet. On that spreadsheet, I had formatted the x-data column to only 1 decimal place. when I copied and pasted the data to Origin, the data was truncated to one decimal place. This is why Origin was seeing a non-uniform data spacing. I simply removed the formatting in my spreadsheet (i.e. no longer required 1 decimal place) and this time when I copy and paste the data it worked fine. So I guess I'll have to be more careful when copying data from a spreadhsset in the future to make sure that the data does actually get passed correctly. Thanks for the help.

Cheers,

Greg
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zachary_origin

China
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Posted - 11/30/2006 :  10:24:38 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Just a reminder. You can directly open a Excel file in Origin. Select File: Open Excel. Then there will be dialog to let you choice open as an Excel workbook or an Origin workbook.

Zachary
OriginLab Technical Services.
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