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morad85
Jordan
6 Posts |
 Posted - 05/03/2017 : 07:53:38 AM
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Hi everybody,
I have two data readings for the same experiment but there is a deviation between them as shown in the attached graph.
How can I make them the same so that I can get the same slope for the linear parts. (in other words, I need to match the slopes where the x-axis range from 1 to 5). Assume the new graph is the correct one
Best regards,
<font color="purple">Morad</font id="purple"> |
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arstern
USA
237 Posts |
Posted - 05/03/2017 : 10:35:58 AM
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Hello,
To set the old data to have the same slope as the new data, you can first find the slope of the new data and then create a linear fit for the old data with the same slope at a certain x -range. (note: looking at your graph, you may want to use a nonlinear fit, that's something you will have to test out)
To do this:
1) Find the slope for the new plot between an x range:
You can use the Linear Quick fit Gadget: http://www.originlab.com/doc/Origin-Help/QuickFit-Gadget. You can set the gadget to find the slope between x = 1:5 by dragging the yellow box.
2) To create a fit you may want to set the curve to fit through a certain point i.e. at the point where x = 1. You can use a direct weighting method. http://www.originlab.com/doc/Tutorials/Fitting-FixThroughPoint
Create a new column next to your old XY column data. For this new column set it as a y-error column. Input into the rows a small error value i.e. 0.01, except for at the row where you want to set the line through a certain value (i.e. x = 1), input a larger error value that will stand out. i.e. input the value 1.
3) Next, select your old data points on the graph and select Analysis --> Fitting. Select Linear Fitting. With the Linear Fit dialog box open, select --> the Input Tab and select--> By X for the Rows Tab. Input your range of x values i.e. From 1 to 5.
Select the Fit Control tab and select Fix slope. Input the slope value that was retrieved from the step 1. Select --> Direct Weighting tab for Errors as Weights.
For the fitted curve, if you want to have the same number of points from your old data: Under the fitted curves plot tab, under the X Data type tab ---> select Same as Input Data tab.
--Aviel
OriginLab |
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morad85
Jordan
6 Posts |
Posted - 05/04/2017 : 02:12:51 AM
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So many thanks for the useful information!
Cheers,
Morad.
<font color="purple">Morad</font id="purple"> |
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matching two slopes