Curve fitting non-linear with string formula

Similar Questions

• Non-linear curve shape VI don't, get error-20068

  Hi, I have a problem of raw data to a formula of mounting. The formula is f (x) = - ax + b + c (x/d) ^ e. I use the non-linear curve Fit VI, Lev - Mar: the formula string. I'm able to calculate 4 5 parameters (a, b, c and d). I can't calculate, but it should be around 10. When you run the VI, it gives me "error-20068 occurred at NI_Gmath.lvib:LM get new coefficients.vi:1. " "Analysis: input parameters has at least one element that is Inf, NaN, DBL_MAX or DBL_MIN"

  It is tracing the equation based on the initial settings without actually finding the best adjustment of the parameters. I also tried using the VI version to create the formula, but it gives me the same error. What can I do to avoid this error? I have attached the vi and a data file.

  

  Some of your top X values are negative. Remove them and things will work fine.

  (You get a negative signal for the exponentiation, which is allowed if the entry is complex or the exponent is an integer. This isn't the case here, where the exponent is not an integer. The exponent is an integer in the first function call, but not more once, trying to calculate the partial derivatives of the model. Try with a hypothesis of 9.9 instead of 10, and it will fail immediately)

• Non-linear curve fit (distribution of blackbody radiation)

  Hello

  In my measurements I would estimate the temperature from the spectra of light emitted through the Planck law of the distribution of the black body radiation. I tried to get my data with non-linear curve fit, but I encountered some problems:

  1.) function is not properly, because of the distribution of different adjusted data form and input data values.

  (2) when tracing distribution of Planck by using the best shape parameter, the plot is different from the theoretical distribution of given temperature. (My data comes from the source of temperature 3100K, best setting made is 1130K, but fit is different from the theoretical distribution of 1 130 K)

  

  When I get a few simple equations, everything works, so I'm not sure of what could be a problem.

  Many thanks for any advice.

  Ivan

  Quickly, giving once more on this, it seems to me that one of your constant if four orders of large magnitude.

  You get a very good fit with 3.74177E - 16 instead of 3.74177E-12, see picture. (You divide your theoretical curves by 10000, but you aren't in your formula!)

  

• Non-linear curve Fit error 20068?

  Trying to do a simple 3-exponential decay curve nonlinear.  I have a copy of this work in the other screws, but it doesn't seem to work in this VI.  I use "Scalablemultiexponentialdecay" of Altenbach as a VI/template model.  Data that I'm trying to adapt are a series simple decomposition RC, yes I realize that should not have 3 exponential components, it's just the model data.  I am able to adapt with the Fit exponential function built in to the Math palette, but which only works if the input bounds parameter is wired and with rational constraints.  However, I get an error on the adjustment of the non-linear curve that I understand not (photo attached) indicating that an INF or NaN is done in the settings.  I don't see where this is going...

  Any questions or help is appreciated.

  

  

  I thought so, only 0 s for the 2nd two exponentials.  But, if I replace all the guess seededes with the same as the simple exponential Installer, it converges without error.   I guess I didn't know it was that sensitive.  Thank you.

• Fit Gaussian Peak and non-linear curve Fit on small data differ from the PEAK of origin made

  Hi all

  I'm developing a program in which I have to adjust the curve of Gauss on only 4 or 5 data points. When I use the Gaussian Ridge Fit or adjustment of the curve non-linear, it connects linearly all the points so that other editing software like origin's curve fitting of Gauss on the same set of data that I have attached two images is LabVIEW with Fit Gaussian of Peak and nonlinear adjustment and other is original.

  The data are

  X                       Y

  799.09857 257
  912.25256 641

  1026.00366 1516
  1137.92871 1118
  1253.43713 329

  Interesting.

  The initial default values assume all are NaN, which causes the LV calculate conjecture.  The default values for the parameter Bounds +/-Inf with the exception of the offset that are both zero. This, of course, forces the output zero offset.  It seems a strange fault, but they may have a good reason for it.

  Change the limits of compensation to something else translates the output being offset ~ 215 and the Center moves to ~ 1053.  These correspond the original result to 5 significant digits.

  Lynn

  

• Introduction to the tutorial of curve fitting - curve example of non-linear editing

  As stated in my first question, I asked yesterday I'm new to labview and I always work in the curve editing tutorial, but I am now up to the non-linear section (although I jumped the polynomial stuff for now).  So my question now to do the with the vi illustrated in Figure 14 of the Introduction to the tutorial Curve Fitting.

  My problem this time has do with graphic design for data non-linear Gaussian and adapt.  Looks like it gets its data from a cluster of some sort which is itself drawn to clusters separate construction.  The problem is that I can't find the appropriate function of cluster, which will result in the production of a graph.  I had a test using a variety of different cluster functions and also have a look to try to use a matrix function and none of them work.  Now, an assumption that I did is also that the graph is of the form XY (and not a waveform graph).

  Note that I am aware that part of the problem could be my lack of experience in coding using labview, as I've attached the vi that I worked on.

  I'm using labview 8.6.

  Thanks again for any help.

  Do not use the function you are using.  Use the cluster on each plort bundle, then build the table of these 2 groups.

  To the Subvi, you right-click the entry that caused the broken arrow and choose create constant.

  Whenever you have a problem trying to find the right data type into a Subvi.  Do a right click, create constant.  Now, you will have a default constant of the correct data type that you can modify as needed.

  

• apply restrictions for the non-linear curve fit

  Hello Forum users,.

  I am currently working on a VI control which is supposed to create a specific model of pressure inside a hollow tube to provide a test environment for pressure sensors. The details are many and complicated, so let's say I am sure that my formula to calculate this profile according to the pressures inside the hollow rings around this tube will work.

  To find the correct pressure for each ring values, I've linked to a model VI containing this form to Lev. - Mar algorithm (the non-linear curve adjustment) and let it run.

  Technically, there is no problem and Lev - Mar find values to adjust the function for the values (not perfectly sure, but close enough).

  The problem is, however, that, since the device, once suitable values for the positioning and size of the rings are found, must be built, the simulated pressure rings perhaps intersect not between them. To apply this rule, I added a check to my VI of model and if the values passed to Lev - Mar breaking the rules, the VI model gives a matrix of zeros to follow him (I tried an empty array, but that only leads to error messages).

  This solution did not work. Lev - Mar seems to ignore these cases always looks for values that break my rules (and if I put these values through my model VI, I get a matrix of zeros, as expected, so the audit seems to work).

  Perhaps I misunderstood the algorithm of Lev - Mar and it does not actually check each possible defined coefficients of finds.

  Is it possible to adapt to any function of a set of values while keeping the predefined boundary conditions?

  Oh, before I forget:

  I use LabVIEW version 8.2 in the Institute, because the workshop systems is not installed 8.5 for some reason any.

  Thanks in advance

  Thaliur

  Hi Thaliur,

  Thanks for posting on our forums.

  I understand your request you expect the algorithm to ignore a case to all zeros in the table. However, it is not implemented like this.

  Good news is, its source code can be edited and you could save your own personalized version of the algorithm of screws it is to you that you just add a check for a matrix of zeros or simply pass another parameter which indicates only a case of "broken rules". Then you would not have to continue the calculation.

  If I misunderstood your question, please clarify this. You can also post a code for further explanation, if you wish.

  Good luck with the project!

  Peter

• Error-20003 of curve non linear adjustment LM with a VI curve as a good model

  Hello

  I was stuck for a while now, by an error when I use the non-linear curve mount LM with a VI as the model curve adjustment. The code error is-20003, and occurs in the "LM get new coefficients ' vi and analysis, said"the number of samples must be > 0 ". I checked a number of things, but I can't get rid of it. The VI is quite simple: it uses a database of three sets of numbers (or ghosts) and it aims to adjust a curve that is the sum of these three spectra to determine the multiplicative coefficient associated with each spectrum. The code is attached to this message, thank you so much for any input!

  Looks like your model function has default data stored in the output of f'(x,a).  Try to empty the table (be sure to "Save as default" after emptying) and run again.  This solved the problem on my machine.

  Apart from this specific error, it seems that your model is linear in the spectrum of the molecule, so maybe using Fit.vi linear General is a better match for your problem?  The two algorithms give the same results on my machine.

  -Jim

• Non-linear curve fit the model of reference file

  Hello.

  I use the VI of the non-linear curve adjustment in order to adapt the data. The reference to the fitting VI model I use is included in the attachment. You can see that I have a few constant wireline, like 4, 2500 and 1. I want to do this constant variables I'll change before each curve corresponds, because actually in my problem this variables I know before the adjustment and they are constantly changing, and for the moment this made VI just to test.

  The problem I have is that I can't enter the values of this variable to my main VI, where I also call the VI was nonlinear. The scheme of connection of refernce VI made must be changed in order to be recognized by the VI was nonlinear. I tried to use a table to transfer variables, but if I use one, it recognizes the variables as parameters of editing and he's trying to install as well in the adjustment process, and it gives me erroneous results.

  Any ideas how I can add the values of variables?

  Thank you very much.

  Kind regards

  Nikola comedy

  To provide additional data randomly in VI of model, you must use the entrance of 'data' (it is a variant and so can contain anything you want!). Just create any type of data you want (generally a cluster if there are several values of different data types) that contains all the values, convert them to a Variant in the main VI and the variant of wire to crimp her. In the model, you convert the variant return to data, to the constant help of cluster, such as defined in the main as VI 'type' (simply right click cluster in the main VI... wire Create constant... move the constant in VI of model). Now, to unbundle the different values and use them anywhere inside your model.

• The non-linear curve fit lev mar problem

  Hi, I have a set of 10000 readings recorded every second. My goal to draw these vs time readings (1-10000 s) in logarithmic scale and adjust the exponential curve that results with my model equation: a1 * exp (t * b1) + a2 * exp (t * b2) + a3 * exp (t * b3) + a4 * exp (t * b4) and get the values of the coefficients (a1 to a4, b1 - b4). I changed the non-linear adjustment of lev - mar.vi according to my model. However, I ran into a problem.  I get the following: error-20041 occurred at LM.vi:5 to get on the curve of the NI_Gmath.lvlib:Nonlinear Possible reason (s): the system of equations can be solved because the input matrix is singular. I can't work on why I get this error. I enclose 3 files: the data file (values of Y), X = 1-10000; coating not get my model and vi vi.

  I'm using Labview 8

  I would appreciate your help and suggestions! Thank you very much in advance. ANU

  Hello

  @Jim-thank you very much... ur modified vi helped a lot... but a strange thing on the adjustment is that it depends a lot on the estimation of the coefficients... my model should have values of 'a' coeffs in the order of 10 ^-7 and 'b' should be higher around 10 ^-1. The initial proposal is amended the best coefficients made vary accordingly.

  I don't really know if this can b fixed... I enclose my vi.

  VI: - non - linear adjustment model, exponential branch.

  data - pol.txt

  I appreciate you all!

• The non-linear curve slope

  Hi all

  How can I get the slope of a particular point in the non-linear curve? I use Lev - Mar curve fitting is not linear.  The slope is to determine the dynamic resistance of the current-voltage curve of diode if dynamic resistance = 1/slope. Kindly help...

  
  

• How to calculate the equation of dataset using 'Fitting VI' (non-linear or polynomial fit)?

  I have the datasheet of a NTC (thermistor negative Coefficient) and I want to calculate the most approximate equation

  that describes its behavior. The table has values of temperature and resistance. If the resistance of the NTC varies according to the temperature it detects. I tried the following:

  -Excel: polynomial adjustment

  -Maple: polynomial adjustment

  -LabVIEW: Polynomial Fit.vi

  I've been doing equations with a not very good approximate parameteres. I suspect that this method 'Polynomial FIT' it is not the best method for this type of data/equation (being a non-linear equation).

  So is - that someone has used the non-linear Fit.vi matching the behavior of a dataset object? If so, can you explain how this VI... I would really appreciate it.

  Thanks in advance and I will wait for your reply.

  
  

• Adjustment of the non-linear curve - maximum iterations exceeded (error-23026)

  Hello

  In my application, I use the curve non-linear adjustment VI (Levenberg-Marquardt) to adapt the data acquired continuously using a task DAQmx. Often in the course of the implementation of the instrument, the curves are not yet "adaptable" and max iterations set in the parameters of expiration is reached.

  It's OK but the problem is that it generates an error (-23026) that stops the execution of the VI.

  How can I ignore this error and continue to run the VI until the termination is controlled by the setting of tolerance?

  Kind regards

  Bernard

  Hi Bernard,.

  Need to wire the error output and handle the error programmatically.

• Non-linear adjustment of voltage vs Angle data

  I am trying to create a curve Labview VI that I get error 20068 for which is "analysis: input parameters has at least one element that is Inf, NaN, DBL_MAX or DBL_MIN. I have attached my data file "Peak.csv" that I use to adapt to the curve, as well as the vi, "fitting.vi."

  Here's what I noticed, this is incorrect.

  1. the X values seem to count up to 1500 (the number of values that I have x) despite the fact that I Wired X output values to the nonlinear adjustment function. Is it supposed to do this? How can I wire the vi so that the adjustment is in fact values of 70 to 85 degrees (slices de.01 degrees that is why it is 1500 points) as opposed to simply fitting the number of values without taking into account their individual values x?

  2. my function "may" be incorrect due to the fact that it is so long, but at this point, I want to eliminate other possibilities because I checked it several times.

  3. my real data on the graph show (despite the fact that adjustment is = if bad, it is difficult to say unless you approach of y 0 to y =. 05)

  This adjustment algorithm is for a thin monitor that uses the equations in the document "Frustrated total internal reflection and application of Its principle in Laser cavity Design" located at: http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-3-6-719thank you very much for your help in advance!

  A useful thing to try when (as from altenbach) editing of data problems is to visualize the data and the model calculations.  When I do that with your data, that's what I get:

  

  Note that the two graphs contain the same data and the same X - xxx scaling. The scales of the y-axis are a factor of 10 ^ 5 apartment! Although you can see in the charts the vast majority of the points calculated by your product formula NaN, which is what you said the error of the fitting VI. Here's an extended overview one of the summits. Observe that there is no less than 70.3 points or more 71.1 for parcel 1, because those who have NaN values which do not draw.

  

  I was not looking to determine what should be the formula but clearly what you have does not match your data.

  I did this calculation with Parse formula String.iv and Eval String.vi parsed formula using the string of formula that you wired to the fitting VI and X of your file values.

  Lynn

• Curve adjustment not linear function

  Hello everyone:

  I'm a little new here and at the same time a new learner for labview. My need for laboratory to adjust the data which are not linear, so, I choose to use the model non-linear curve VI. But when I run the VI, the error is that:NI_Gmath.lvlib:LM formula function.vi:7290001 string, or other displayments of the error. I tried several times, but unfortunately didn't. The problem may be the expression of the function form. Moreover, the design of the VI is not mine, it's Forum OR. Any constructive suggestions will be welcome.

  The form:

  y = Y0 + (Nr * cos (A)) + *(x-W1)/((x-W1) a1 ^ 2 + L1 ^ 2) + a2 *(x-W2)/((x-W2) ^ 2 + L2 ^ 2)

  In fact, the form is very long, I just write some.