Adjustment of curve using Levenberg-Marquardt algorithm

Similar Questions

• Levenberg-Marquardt optimization question

  Hello

  I am trying to use the Levenberg-Marquardt algorithm, using a technique of optimization error percentage instead of the technique of the absolute error. AFAIK the Levenberg Marquardt in Labview algorithm uses the technique of the absolute error (i.e. Y - f(x)) when calculating on the errors. How can I change this option to use the technique of percentage error, when the error = [(Y - f(x)) / y] * 100? I changed the calculation of the error in the algorithm to calculate the error in this way, but the results were not satisfactory. I wonder if I forget something or there at - it much more to what meets the eye? I know that in other programs like Mathematica you can choose how you want the error calculated, but I do not see this option in the Labview vi. Any help appreciated.

  Thank you

  LMS

  Additional information:

  I'm using Labview version 8.2

  I changed the Subvi ABX to calculate the error differently. The ABX vi contains a Subvi called gradient and function of LM. The output of this Subvi calculates better suited like Y - the error. I changed this calculation to be [((ajustement Y-meilleur) / y) * 100] to obtain the percentage of error instead. This affects alpha, beta and chisqr. I think I may need to make other changes to the algorithm to implement the technique of error in percentage but I don't know what changes to make. The results that I have received the above changes were worse than the results I got from the method of the absolute error (error = Y – the better suited). This should not be the case. I implement the VI of the Levenberg-Marquardt algorithm format and not the string of the formula. Any help appreciated.

  Thank you

  LMS

  Hi LMS.

  I don't know if I understand.

  However, as the Lev - Mar algorithm calculates Y - f (x). If you divide that result by the best linear fit (Y) and multiply by 100. This will give you your desired effect.

  I hope this helps you.

• How to track the progress of Levenberg-Marquardt

  Hi all

  My Levenberg-Marquardt works perfectly, but one iteration takes quite long, about 5 seconds, as expected from the complexity of my problem (~ 50 parameters fit).

  Question: How to display the current number of interaction in the main program, for the user to know that it is still ongoing?

  (My solution so far is to put a probe in the Levenberg-Marquardt subroutine provided on this 'i', which is the current interation. "But it's not easy to use).

  Thanks & best regards!

  Peter, LMU Munich, Germany

  You can use your model VI to increment a counter that appears elsewhere. If your model compute partial derivatives, then there will be only one call per iteration LM model VI plus 1 for the estimate.  If you are not calculating the partial derivatives LM then uses central difference method to calculate them.  This means function by iteration of LM 3 calls, plus 3 for the estimate.

  -Jim

• Samplers colour - dark, clear & grey point - how to adjust the curves

  Hi all

  I set myself dark, light & gray point in an image. Ask yourself how to adjust the curves based on the color samplers. I manually call the dialog box curve and select the dark feather and choose sampler no1, select cast and select no2 sampler, select gray feather and choose sampler no3. No idea how this can be done in the script?

  OK, I see one of the problems, and you noticed yourself, you just did not understand what is happening.  When using the pipettes in the curves Panel it does not matter if you use the black or white pipette first. You can set the white point and black point or reverse that order and you get the same curve. What is important is when you use the grey eyedropper. That should be used when both the white and black point has been resolved. If you set gray in the Middle, he gets thrown when you set the last point and you get the same curve, if you simply ignored the gray point total. In other words, if you do not set the last gray point said you in effect it at all.

  Notice in your video when you click on the sampler on the neck that the image is very cyan. It is only when you click the last sampler that color refers to something more normal. You can see the same thing in looking at just the curves. By clicking on the neck creates curves with long arcs. By clicking on the last sampler transformed into lines between the white and black point (because the gray point is deleted)

  Which brings back us to where the sampler are placed make a big difference. Skin tone is not when you want to set the gray point. I think you are using the mask of the luminance to calm the adjustment because the black and white points are also misplaced. The color of the blackhead is within 20 years. I think a better place would be under the jaw on the right side of the neck. Indeed, this region is already 0,0,0 so I would not put a black dot. The white Sampler is in 230 years. Parameter to white clips many of the wall at the top left.

• How to sweep the IV curve using instruments GPIB (ILX 3220)

  Hi, I'm new to Labview - I learned basic stuff, such as strings, arrays, structures, etc. I have a source of current ILX-3220, OR-488. 2 and I want to do a curve using one - light-emitting diode. I'm really confused about what I should use. I downloaded the drivers from the site Web of ILX intrument. They provide examples of screws, but I can only define a stream and read voltage. I try to configure the block schema by adding a loop, then I got lost among the SubVIs complexes. I also tried to use IO tool Wizard to connect with the power source, but apprarently he didn't listen to me . I can input the commands one by one (LAS: LDI 5 LAS: LDV?)  LAS: LDI LAS 10: LDV?...) -not much differently to write down by hand. Is it possible to scan the IV of ILX 3220 curve?

  Yes, you can use a loop - either a loop for or while loop. I'm not familiar with the instrument or functions, but at the very least, you should place the function that defines the current and the function that reads the voltage inside the loop. The loop would probably have a registry change and you would be this thread to the current set function. Inside of the loop would be a function increment and little code to determine if the maximum intensity has been set. Here is a generic application of ramp.

• adjustment of curve with the equation

  I have a program in which I receive a response signal which is of the form A * cos (w * t) * exp(-t/T2), where A is the amplitude, w is frequency, t is time, and T2 is the spin relaxation time. Is it possible to adjust a curve in this graph and output the values of the variables? I have tried many options in labview but can't seem to find a way to add the variable T2.

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• Smartphones blackBerry re - adjust the curve?

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• How do Control M to create an adjustment layer curves?

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• Both of these tools use the same algorithm?

  Database (TimesTen) in memory of Oracle and Oracle coherence they use the same algorithm?
  Two of them are databases in memory?
  Otherwise, what is the difference?
  
  Published by: qck on August 11, 2009 20:17

  No, they are different tools, and they use different algorithm.

  Oracle TimesTen in-memory database is a relational database memory-resident. Deployed in the application as a layer
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• Adjustment of Levenberg-Marquardt tweaks

  Hello

  I have two questions about the non-linear curve fit LM VI:

  (1) does anyone know why after one iteration successfully the lambda value is multiplied by 0.4 instead of 0.1 as in the implementation of the standard (i.e. Numerical Recipes)? This factor has an influence on the speed of the adjustment?

  (2) is it possible to use analytical derivatives to speed the evaluation of the slope and the Hessian of Chi-square?

  Thank you

  Bernard

  (1) maybe it's so nobody is accusing them of use directly the NR without attribution.  That the value is just an empirical assumption, so there is nothing too magical about 0.1 or 0.4 (better to be less than 1).  As you have found where this value is used (not too hard), I suggest that you experience in the changing of 0.1 or 0.2 or 0.5 and see if that makes a difference.  Let me know, I have not tried.  When I implemented the systematic NR in LV, I used 0.1 and it worked, and when I use the LV routine with 0.4 it still works.

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• Problem to adjust the data using the algorithm of lev - mar...

  Hello

  I'm a casual user of LV, and I need signal level using a non-linear custom model. The signal is basically a decay of exp (order 1) with a continuous component, so it's pretty simple.

  When I apply the routine of Lev - Mar's non-linear editing, I've always had the famous "an exception has occurred in externally called by a function of the call library node. This could have corrupted memory of LabView. Save any work., etc.. VIwas stopped to node "" a call to "NI_AALPro.lvlib: Real - Decomposition.vi of SWINE vesicular disease.

  The thing is I've already adapted successfully some basic (linear model) data using this form of Lev - Mar non-linear... but it won't work this time... and I don't see why.

  Could you watch my VI and model definition and tell me what I need to improve, and what might cause the problem? The main VI (TPV_Fit_ExpDec1_v1.0.vi) open a text file that contains my data (3 columns: time, a pulse (not useful for editing), the signal to fit). At the beginning, I isolate the part of the signal that matches t > = 0, because it is where begins the exponential decay. So I want just to get the part. I join the main VI, a txt file containing typical data, and made the VI that define the model to the lev-mark function.

  I would appreciate your help and suggestions!

  Thank you very much in advance.

  MY VERSION of LABVIEW is the 8.2

  JB

  Here's a quick rewrite. You should ALWAYS figure the curve for the initial parameter estimates see if they are in the ballpark. Rather than modify the data, you could just put the weight to zero for negatvie x. see if it works better.

  

• Levenberg Marquardt adjustment: problem of formula

  Hello

  I'm so new to LM did I maybe a stupid question... Please bear with me!

  I try to adapt a simple formula but routine LV tells me my formula wrongly.

  is attached a PNG for my case!

  Thanks for any help

  concerning

  N

  Without looking at the help, I'm not sure but check if the formula is case-sensitive.

  Lynn

• Adding points to the adjustment layer curves in PsCS6 broken?

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  Is a kind soul able to tell me the correct key combination to achieve the desired result, or is there really a problem with CS6?

  Post edited by: hienromaric

  It should be documented here:

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• BlackBerry smartphones restore Conact on the new curve using back to the top of the old

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• How will I know if an adjustment is in use?

  First Elements 14.

  I select a video clip, then at the top right, I use Adjust > color > Vibrance > I click on one of nine thumbnails > the clicked tile shows a highlight that surrounds > in the display window, I see the clip change. Then I work on several other clips.

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  If you click on the "show more" link, you will see cursors indicating the setting.