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 Integral of several curve		  New Topic  Reply to Topic
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Mr.PV

Switzerland
1 Posts
Posted - 04/17/2016 :  4:46:57 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. and Service Release (Select Help-->About Origin):
Operating System:

Dear all,

I have two problems with this curve.

1) I need to calculate the integral of the upper positive and negative part, and I want to have the two values separately. The quick integral calculate the full integral of the graph, giving as result the difference between the upper and lower part.

2)The second problem is that I have a lot of this curve so I would find a way that calculate the integral all together. For this reason I did not separate my data in positive and negative part and consequently calculate the integral of each part.


Best,

Mr.PV

Hideo Fujii

USA
1582 Posts
Posted - 04/18/2016 :  4:30:24 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Mr.PV,

One possibility is as follows. As I didn't want to bother you to find and insert the coordinates of points
at Y=0 to the original worksheet by interpolation manually, it may be "practically" workable.
1) From your original data, perform the Trace Interpolation (under the "Analysis: Mathematics" 
   menu) with very large number of output points, say 1000. (Make sure that the Recalculate mode  
   has been set to None.)
2) Highlight the new Y2 column, and add a filter, and set the condition to greater than 0.
3) Perform the Polygon Area (under "Analysis: Mathematics).
4) Change the filter condition to less than 0, and get the polygon area again.
I think this procedure is well routine-like, but if you need to automatize the process for bunch of data,
you probably need to make a script.

(Note that there seems a bug in Origin 2016 which prevents you set to beyond 1690 points by the
trace interpolation. This bug should be fixed in a later version.)

Hope this helps.

--Hideo Fujii
OriginLab
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DennisHailey

1 Posts
Posted - 06/22/2019 :  05:52:22 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Just as the definite integral of a positive function of one variable represents the area of the region between the graph of the function and the x-axis, the double integral of a positive function of two variables represents the volume of the region between the surface defined by the function (on the three-dimensional ...
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