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mwm25
1 Posts |
 Posted - 07/22/2009 : 9:50:35 PM
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Hi,
I plotted some data points that form semi-circle. But the semi-circle is not complete, i need to extrapolate until it intersects with the X-axis. I tried Analysis - Mathematics - Interpolate/extrapolate function but it did not work. I also tried polynomial fitting but I did not get the curve extended to intersect with the X-axis.
Do you have an idea how to do it?
Thank you!!
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VincentLiu
China
Posts |
Posted - 07/23/2009 : 05:31:03 AM
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Hi mwm25,
Do you mean you just want to fit part of the data (the data in the semi-circle which bounded by the red rectangle in the following image)?
And want the left part of the interpolated curve to intercept with x axis? If this is not the problem, please give us more details about it. And please also send the data through
http://www.originlab.com/www/company/qform.aspx?s=1&
Best regards,
Vincent
OriginLab Tech Services
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Edited by - VincentLiu on 07/23/2009 05:34:42 AM |
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easwar
USA
1964 Posts |
Posted - 07/24/2009 : 12:06:42 PM
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Hi,
We received your files and will send you an answer. To update others who may be interested a fitting can be done to such data by defining a semi-circle fitting function such as below:
y = y0 + (r^2 - (x-x0)^2)^0.5
And then if the spike points are masked and x0, y0, r initialized properly, the function will fit the data well. The semicircle can be extended to the right by setting custom x values for fit curve in the NLFit dialog, or by extending the X axis and asking the fit curve to span the full axis.
Easwar
OriginLab
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Birdman
Uruguay
Posts |
Posted - 07/27/2009 : 6:46:01 PM
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Hello, Can somebody help me with this?
I am traing to graph the following equation in a origin plot
N(t) = t - pi^2/6 - 2* (sumatory (between infinity and n=1) of (1-)^n/n^2) * exp(-n^2*t), How can put the equation to obtain the plot?
thanks in advance
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larry_lan
China
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Posted - 07/27/2009 : 9:30:59 PM
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Hi:
Could you please start this question in a new thread? And are you sure the equation is correct?
N(t) = t - pi^2/6 - 2* (sumatory (between infinity and n=1) of (1-)^n/n^2) * exp(-n^2*t)
You'd better upload an image for the equation.
Thanks
Larry
OriginLab Technical Services |
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chithrastar
India
1 Posts |
Posted - 03/30/2013 : 03:21:42 AM
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Hi,
In order to fit semi circle, which option in origin8 I have to choose for inserting the semicircle function given here. Please help me.
chithra |
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snowli
USA
1383 Posts |
Posted - 03/30/2013 : 4:02:02 PM
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Hello,
In Origin 8, choose Tools: Fitting Function Organizer.
Click New Function button and then edit the fields to define the semi-circle function.
E.g.
Function name: semicircle
Parameter names: y0, x0, r
Function Form: Origin C (keep the default setting)
Function:
y = y0 + (r^2 - (x-x0)^2)^0.5
Click the small icon to the right of Parameter Settings box to define initial values, etc. of the parameters. //Please make sure some initial value are given.
Click Save to save the function.
Then select the Y data or plot the data and open NLFit dialog.
On Settings tab, choose the Semicircle function to fit your data.
Thanks, Snow Li
OriginLab Corp. |
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jamesboy
1 Posts |
Posted - 03/04/2014 : 12:12:23 AM
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Hi,
I want to fit many datum by origin 8 with one single circle to find the radius.
I have tried the method mentioned by snowli, but I got "Fit did not converge - reason unknown".
Could anyone help about this?
the data can be download here:
http://tinyw.in/XfVa
Thx a lot !!
james |
Edited by - jamesboy on 03/04/2014 09:50:50 AM |
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Topic |
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Curve Fitting