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Ducciolo
Italy
4 Posts |
 Posted - 08/10/2021 : 07:07:47 AM
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Origin 2020 (64-bit) 9.7.0.188
Windows 10
Hello! I am trying to fit my data with a gaussmod function. It works well if the skewness is on the right side, but the preset function cannot recognize a skewness on the left side. I already tryed to change the bounds for t0 in the fitting windows (e.g. t0<0,...), but then the fitting won't work at all. Can you please tell me what should I do/change in the preset gaussmod function to make it fit a left-skewed distribution?
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YimingChen
1609 Posts |
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Ducciolo
Italy
4 Posts |
Posted - 08/11/2021 : 03:59:59 AM
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| Yes, I saw that and I tried to solve the problem by removing the lower bound for t0 and putting an upper one with t0<0. But the fitting didn't work. |
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Sam Fang
293 Posts |
Posted - 08/11/2021 : 05:42:13 AM
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Hi Ducciolo,
If t0<0, there will be no peak in the curve. Do you think it makes sense?
Origin's Fitting Function Library app provides a function GaussModP6,
https://www.originlab.com/FileExchange/details.aspx?fid=490
which supports t0<0. You can remove the lower bound for t0 first and try.
Sam
OriginLab Technical Services |
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Ducciolo
Italy
4 Posts |
Posted - 08/11/2021 : 09:21:38 AM
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| I tried the GaussModP6 with t0<0 and also changing the other parameters but the fit don't work as well. It is like the function do not allows a skew on the left side but only on the right one. |
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Sam Fang
293 Posts |
Posted - 08/11/2021 : 10:32:01 PM
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Hi Ducciolo,
Can you send us your data? We can try it.
To see how to upload a file, you can click Send File to Tech support button on the top right of this page.
BTW if this function can't fit your data well, can you choose other functions?
Sam
OriginLab Technical Services |
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Sam Fang
293 Posts |
Posted - 08/12/2021 : 10:04:43 PM
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Hi Ducciolo,
You can remove lower bounds for t0 and w in the app's GaussModP6 function, and choose an initial values of t0<0 and w<0, you will find the curve becomes left skew.
Sam
OriginLab Technical Services |
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Ducciolo
Italy
4 Posts |
Posted - 08/16/2021 : 04:23:23 AM
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| Thank you all a lot for your time and suggestions! It is working perfectly now. |
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Sam Fang
293 Posts |
Posted - 08/25/2021 : 04:49:51 AM
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Hi Ducciolo,
We added GaussModLeft function in Fitting Function Library app:
https://www.originlab.com/FileExchange/details.aspx?fid=490
Fitting Function Library app is pre-installed in Origin. If you can't find the app in Origin's App Gallery window, you can install it from the above page.
Launch the app, choose GaussModLeft function in the opened dialog (in the last row), click Download button, and GaussModLeft function will be installed in your Origin.
Using this function, you needn't use a workaround. This function is a convolution of an exponential growth function with a Gaussian function. And the skewness is on the left. Here t0>0, w>0.
Sam
OriginLab Technical Services |
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Topic |
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Gaussmod fitting help