Multiple Gaussian Peak Fit for Wavelength Spectrum

Hello.....
First, let me confess to being a relative noob..... So please be gentle.
I am trying to create a vi to analyse an optical spectrum of the form: Intensity vs. Wavelength. This vi would need to do the following:
1: Read the input data file.
2: Set a noise floor, below which all data will be ignored.
3: Scan the spectrum and identify the amplitude, width, and center of any peaks that are above the noise floor. There will be multiple peaks present (as many as thirty or so).
5: Fit a gaussian to each peak.
6: Sum the gaussians and create a new data file from this sum.
So..... I know what I want to do, just not the best way to do it. Is there a vi already in labview that will do this for me? The Gaussian fit vi seems only really useful if you want to fit a curve to a single peak. If I need to build this from the ground up, which is fine since I need the practice anyway, what would be the best way to start?
Thanks in advance for any help.
nia

Hello Nia,
There are many ways to approach this problem. By chance, do you have access to the sound and vibration toolkit for labVIEW (http://sine.ni.com/nips/cds/view/p/lang/en/nid/209056)? That toolkit will make performing the signal processing tools which will make creating this VI much easier. The following links may also be helpful for getting started with your issue
http://zone.ni.com/reference/en-XX/help/371361J-01/glang/file_vis_and_functions/
http://zone.ni.com/devzone/cda/epd/p/id/5742
http://zone.ni.com/reference/en-XX/help/371361J-01/lvanls/signal_processing_vis/
https://decibel.ni.com/content/docs/DOC-4475
https://decibel.ni.com/content/docs/DOC-17986
http://zone.ni.com/reference/en-XX/help/371361H-01/gmath/gaussian_peak_fit/
Thanks
Doug W
Applications Engineer
Applications Engineer
National Instruments

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Multiple gaussian peak fitting

I have LabVIEW 7.5 How do I fit multiple gaussian peak (amplitude) with Labview. Is there a package to do this or do I have to start from scratch.
Thanks

I don't think there is a LabVIEW 7.5.
Fitting multiple peaks is necessarily ambiguous because there will always be multiple solutions (e.g. swap all parameters of two peaks and you'get an equally good fit). It will be important to have good initial guesses.
An amplitude alone does not define a gaussian peak, each peak also has a position and width so you'll have to fit three parameters per peak. Is the number of peaks fixed or can it be variable? Do all have the same width?
The nonlinear fitting VIs have been extensively revised with LabVIEW 8.0. Doing the same in LabVIEW 7.x would involve quite a bit more work. LAbVIEW 8.0+ even includes an example that demonstrates fitting a function that is the sum of three gaussian peaks plus an offset. That example would be a good starting point for you.
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Gaussian Peak Fit and Nonlinear Curve Fit on small data differ from Origin Peak fit

Hi all,
I am developing a program in which I have to fit Gaussian curve on only 4 or 5 data points. When I am using Gaussian Peak Fit or Nonlinear Curve fit, it linearly connects all the points while other fitting software like Origin is fitting Gaussian curve on the same set of data I have attached two images One is from Labview with Gaussian Peak Fit and NonLinear Fit and other is from Origin.
Data is
X                       Y
799.09857      257
912.25256      641
1026.00366   1516
1137.92871   1118
1253.43713   329
Labview user
Solved!
Go to Solution.
Attachments:
Origin_Fit.PNG ‏21 KB
Labview_fit.PNG ‏15 KB

That looks like a plot of the input data.
When I run it with your data I get a Gaussian curve which looks much like your Origin plot.
The Plot 2 curve is from 128 points equally spaced along X and Y calculated from the Gaussian formula in the LV help using the output parameters from the fit. Plot 1 is the Best Gaussian Fit output from the fit VI. It only has five points.
I used default values for everything except X and Y.
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Does anyone know how LabView determines standard deviation on their Gaussian Peak Fit VI?

The VI reports standard deviation that is quite high. I am wondering if they go out to 5-sigma or something along those lines.
If anyone has had this same issue, please let me know
Thanks in advance!

Interesting you mention the robustness of the algorithm. I have heard in the past that it is not very good. In fact, the data you feed into it must be VERY Gaussian otherwise the fit is just garbage. Luckily for me, my data is quite clean, see the attached picture.
You also mention Levenberg-Marquardt. Is a VI available somewhere or would I need to write my own?
Thanks for your prompt reply!
Attachments:
GaussFitAttachment.docx ‏26 KB

How to fit multiple guassian peaks ?

Hi,
I have a two column data set (x,y) that contain large number of Gaussian peaks ( several hundredes infact). You can think of it more like a wavelength spectrum. The number of spectral peaks is not known exactly. There is no problem in detecting the peaks as they are of same amplitude. Eventually I want to fit a Gaussian funtion to each of these spectral peak and obtain the the parameters such as amplitude, line-center and sigma. This seems a somewhat tricky in LabVIEW. There is an example ( Sum of 3 Gaussian with offset) that comes bundled with LabVIEW. This example VI however uses a static refrence to a model function which is sum of three gaussian curves. This works well for few number of peaks in the data. If we have large number of peaks ( e.g spectroscopy data) then creating such a model function for a large number of peaks is nealy impractical. Is there a better way to handle such peak-fitting problems in LabVIEW? Would greatly appreciate if someone could point out any existing LV code/library function.
Regards,
RK
Solved!
Go to Solution.

Many Thanks Altenbach. That was something I was after. I've attached an example data file of the sep...
Regards,
RK
Attachments:
multi-peak-spectra.txt ‏1128 KB

Gaussian and Lorentzian peak detection for spectroscopy

I am trying to automate some data analysis for a large number of Raman
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Scott Williams wrote:
>
> I am trying to automate some data analysis for a large number of Raman
> spectra, and would like the option of using a Gaussian or Lorentzian peak
> fit (the included VI is some sort of a parabolic fitting algorithm). Is
> there a way to do this with any of the VIs in the full development system
> (or has anyone already made such a VI), or am I going to need to just write
> some C code and use the code interface node?
On my web site you can download a routine that makes a fit to a
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Go to www.originalcode.com, then click on Example Code, Utilities,
and Downloads.
Dave
David Thomson 303-499-1973 (voice and fax)
Original Code Consulting [email protected]
www.originalcode.com
National Instruments Alliance Program Member
Research Scientist 303-497-3470 (voice)
NOAA Aeronomy Laboratory 303-497-5373 (fax)
Boulder, Colorado [email protected]

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Getting errors in Guassian Peak fitting

Hi all,
I am trying to fit Guassian curve on following data
Index
Value
12
237
13
214
14
214
15
218
16
254
17
236
18
271
19
243
20
278
21
282
22
272
23
296
24
309
25
312
26
337
27
342
28
344
29
344
30
358
31
373
32
425
33
432
34
436
35
466
36
508
37
553
38
596
39
613
40
663
41
701
42
744
43
808
44
859
45
924
46
988
47
1059
48
1188
49
1299
50
1415
51
1542
52
1631
53
1775
54
1929
55
2018
56
2225
57
2458
58
2679
59
2956
60
3229
61
3408
62
3666
105
3546
106
3286
107
3023
108
2789
109
2598
110
2385
111
2187
112
1986
113
1841
114
1701
115
1616
116
1485
117
1356
118
1271
119
1165
120
1084
121
1013
122
945
123
884
124
827
125
785
126
721
127
660
128
620
129
606
130
581
131
535
132
519
133
500
134
462
135
438
136
449
137
426
138
381
139
375
140
366
141
338
142
342
143
335
144
302
145
313
146
293
147
291
148
282
149
276
150
275
151
280
152
269
153
255
154
250
155
252
156
248
157
252
158
255
159
242
But Guassian peak fit vi is fitting curve only for one side lobe. result is attached. Can anyone tell me how to avoid this problem
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Attachments:
Fit.png ‏25 KB
data.xls ‏21 KB

Try specifying an initial guess. I used:
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initial center = 80
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initial offset = 200
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