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BryanK
Canada
26 Posts |
 Posted - 11/23/2014 : 5:11:16 PM
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Origin 9, Windows 7
I was wondering if anyone could recommend a good piece of code / function to find the attached point on a series of graphs. 
I was thinking that this is a point of inflection and there is an ocmath_find_inflection_point function, but I don't understand all the parameters, namely xc and w. Is this the correct function to locate the point in red (or the closest data point to it)?
Is there a better way to locate this point?
Once I have identified the x coord, I will set that as my zero via a horizontal shift so all plots show the same start regardless of the raw x-axis.
Thanks for your thoughts,
Bryan |
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Kathy_Wang
China
159 Posts |
Posted - 11/24/2014 : 03:56:07 AM
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If you know the Y value of the point, you could use the levelcrossing tool in Origin:
http://www.originlab.com/doc/X-Function/ref/levelcrossing
Otherwise, you need to know the criteria to define the point, for example if it is an inflection point, its second derivative should be 0?
Kathy
Originlab |
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BryanK
Canada
26 Posts |
Posted - 11/24/2014 : 07:02:52 AM
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Thanks for your reply Kathy.
The exact value of Y also changes. What I do know is that this point (or location) is always about 2/3 less than the peak of the maximum (shown on the curve).
If I use this levelcrossing tool to 2/3(max(y)), it could work. Is it possible to automate this tool with BatchImport?
Best,
Bryan
quote:
Originally posted by Kathy_Wang
If you know the Y value of the point, you could use the levelcrossing tool in Origin:
http://www.originlab.com/doc/X-Function/ref/levelcrossing
Otherwise, you need to know the criteria to define the point, for example if it is an inflection point, its second derivative should be 0?
Kathy
Originlab
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lkb0221
China
497 Posts |
Posted - 11/24/2014 : 10:29:30 AM
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Hi, Bryank
maybe you can try doing a differentiate on this signal and find where the max value of 1st order derivative is.
Zheng
OriginLab |
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Locate data point nearest inflection point