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 interpolation to reduce data?		  New Topic  Reply to Topic
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mwarner

USA
30 Posts
Posted - 03/24/2005 :  12:54:11 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Version (Select Help-->About Origin): 7.5 SR5
Operating System:2000

I have a data set that takes on the following form:
X / Y

400.23/ 0.377
400.59/ 0.397
400.96/ 0.415
401.32/ 0.44
401.68/ 0.463


and would like to reduce this down to simplified X values (e.g. 400, 401, 402 etc.) by interpolation. Any suggestions as to how I can do this in Origin?

Mark

Mike

USA
357 Posts
Posted - 03/24/2005 :  2:18:56 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Mark,


  1. Plot your data as a scatter plot, then choose Analysis:Interpolate/Extrapolate. This opens the Interpolation dialog box.

  2. Choose your Xmin and Xmax, then calculate the Make Curve # pts so that you get the even increment that you are looking for, and click OK.

  3. When the interpolation curve plots, right-click on it and choose Go to InterExtrapn. This opens a worksheet with your interpolated data.



Mike
OriginLab
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mwarner

USA
30 Posts
Posted - 03/25/2005 :  09:17:58 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks Mike, but this is what I have currently tried and it doesn't get me where I need to be. If I set the data points to be 350, I get values starting with 400 that go to 750, but they gradually build up to 750 by increments of 0.286. What I need is interpolated Y data for 400.00, 401.00 etc. while I what I get now takes me further from what I need the higher I go (e.g. I need 700.00 while the current interpolation will give me the Y value at 700.8596). Is there a way to "constrain" the interpolation in this regard.

Mark
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Mike

USA
357 Posts
Posted - 03/25/2005 :  10:28:25 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Mark, let's start with your posted dataset:

400.23	    0.377 
400.59	    0.397 
400.96	    0.415 
401.32	    0.44 
401.68	    0.463

Let's say that what I want to do is to generate an interpolated/extrapolated dataset that starts at X = 400 and ends at X = 402, with an increment of 0.1.

First I create a scatter plot of the data.
Secondly, I choose Analysis:Interpolate/Extrapolate.
In the dialog box that opens, I enter:
  • Make Curve Xmin = 400
  • Make Curve Xmax = 402
  • Make Curve # pts = 21 (this is the number of points that I would have to inter/extrap to get the desired increment of 0.1).


When I click OK, the inter/extrap dataset plots as a red line (default color).
When I right-click on that red line, and select Go to InterExtrapn, a worksheet opens that contains the following data:

400	    0.36422
400.1	    0.36978
400.2	    0.37533
400.3	    0.38089
400.4	    0.38644
400.5	    0.392
400.6	    0.39749
400.7	    0.40235
400.8	    0.40722
400.9	    0.41208
401	    0.41778
401.1	    0.42472
...etc.
...etc.


Isn't this what you are looking for?

Mike
OriginLab
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