General polynomial fitting of a curve at 5 points

Similar Questions

• "Residue" in general polynomial Fit function

  Did anyone of you statistics fans understand how LabVIEW calculates the output of 'residue' in the service of "General polynomial worthy?  How is it related to the R ^ 2 value on a polynomial trendline Excel.

  I tried to figure this out for hours, but aid LV files do not seem to have the info I'm looking for, and I can't find a good explanation on the line.

  Thank you

  FB

  I thought about it.  I was looking at the TOTAL error of all the elements, rather than the average error.

• General using polynomial Fit VI with waveform graph

  Hello gurus,

  I would like to ask how to use general polynomial Fit VI with waveform graph no GraphXY.

  Waveform graph gives me an array of values not X, Y, I think, what do I do?

  Thanks in advance

  Hi Omar,.

  I changed the example Labview embedded to use the general polynomial Fit VI with a waveform graph.

  But why don't you use a X-Y-Graph?

• 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.

  
  

• polynomial fit

  Hey guys,.

  Need some help here.

  I'm a polynomial fit (order 10) for my project. the adjustment takes place between the dielectric constant and the frequency. I made the connection with a block Express Fit and I exported the values in the chart to Excel. The adjustment has been very accurate and the fitted values were very close to the values that I have seen.

  I tried to implement the polynomial equation in a node form and checking the values in real-time by changing my independent variable (x) (Di - electric Constant). When I change the input with control, which should match the values exported from the best graphic made (obtained from the poly block made) right?

  I tried to change my Di - electric values of 1.4 to 5... Up to a value of 3, the output of the formula node averaged exported graphics best fit values. After 3, the values that I get my formula node are very far from the observed reading...

  What is the reason behind this?

  Thanks in advance for your help

  Attached are the VI and the Excel for your reference.

  Hari

  Here is a quick sketch. Maybe this can give you some ideas...

  (Of course the adjustment should only be restored if data or command changes, so it's rather crude at the moment)

• General polynomial adjustment SVD method produces obviously fake bad adjustment

  I use 2009 SP1

  For orders 0-3, it seems to works.  Orders 4 and above to produce results which in so clearly not a better fit, I can imagine how its possible.  I've seen other posts about it, but nobody seems to fully recognize that this is clearly a bug.  Other techniques work well, by eye anyway and completely agree with the other for least square adjustment.

  Can someone explain this?  He NEITHER has a bug report for it?  2010 still has this problem?

  So you can play with the adjustments and watch the nonsense, I enclose a vi with my data set and a loop.

  Floating-point numbers are stored in a mantissa format * 2 ^ (exp), with a certain number of bits to store each.  Let's say that you use m bits to store the mantissa and the exponent n.  As a general rule, the first bit of the mantissa is supposed to be one, so you actually m + 1 bits.  The smallest increment, you can represent is (1/2 ^ {m + 1}) * 2 ^ n or 2 ^(n-m-1).   As the number grows, the increment increases as well, that is why we normally say you have x numbers for a given representation.  Accuracy, as expressed by the magnitude of this figure depends on the size of the number.

  What's my point? Scaling X works in this case because the smaller values X are not exploit fully all the bits at their disposal.  Dividing by say 10 ^ 4 does not effect the accuracy of small representations of number but contributes considerably on the great values raised great powers X.  At some point you start to lose on the small X values and updated information on the scale is more aid.  Then you declare victory, change algorithms, change the representations, the problem of change or move.

  The Givens and master of the House (I always use Householder) changes are inherently effective these type problems (no coincidence why they are popular).  Most of the algorithms include scaling of measures to increase the stability of digital.

• Cursor cross curved in 2 points: find the 2nd point

  Hello

  Here is the emulation of a part of my installation of mesuerement.

  Here are a few points:

  • curve measurement (emulated by sinc function)
  • 2 free sliders UP and DOWN
  • 1 locked cursor 'MIDDLE': his Y is calculated as the average value of TOP and bottom
  • 1 at the crossing can be derived from the Active Cursor (PosX and PosY) property

  There is a simple way to find the 2nd crossing point.

  Thanks in advance

  

  OK, sorry for the diversion of this thread, case 'all' was pretty easy:

  0 # all the:

  

  get the first x position was not too bad

  first:

  

  get the last position x to a level crossing was slightly more difficult but achievable without queues:

  last:

  

  .. .but getting the middle was quite difficult, is there an alternative in addition to using queues?

  median:

  

  Kind regards
  Alex

• Calculation of adjustment of 3 Points 2nd order polynomial curve

  Hi all

  I wonder if there is a simple way to calculate the coefficients a, b and c in a 2nd order polynomial of the form equation

  y = ax ^ 2 + bx + c

  given 3 points known.

  Is there a LabVIEW function that can do this automatically?

  Thank you!

  -FB

  I think you're looking for a general Polynomial fit.

• function with a variable number of cubic curves

  Hello

  I have a set of data : a set representing the independent variable and a set representing the dependent variable. I need to find the minimum number of cubic curves (find their coefficients) that reduce the average quadratic error less than a given tolerance. If the tolerance is higher than 17 particular segments, so I need to raise an error.

  You have an idea what function blocks, I need to?

  I could use general polynomial Fit VI with order 3 and its default method to check the residue. If the residue is greater than the given tolerance, so I could try to use two cubic curves and test them on different starting and ending points until the residue is less than the given tolerance. If tolerance is not guaranteed, I add another curve and I test again the Assembly as shown above. By iteration until the residue is less than the given tolerance, or until I would need to add 18th cubic curve.

  If there was something ready, I would be grateful.

  Thank you.

  Fabiobonelli wrote:

  Please, you can test your VI adding another point to four present?

  X =-6453

  Y =-266

  Check the residue.

  Thank you.

  Did you even read my response? You have a serious air conditioning problem because the data is on a narrow Beach far from zero. By example-6500 ^ 3 is smaller that - 2E11, i.e. a value that many (many!) is orders of magnitude different from that of the constant term (1). The linear algebra problem that results is very ill, conditioned and just blindly Ford over the accelerator pedal are bad advice here.

  This isn't a problem with the implementation of LabVIEW, but a fundamental vice that you encouter also (or worse) If you would do your own math. No way around it. (See also)

  My recommendation is to delete the X offset and add it later again. Now things work correctly. (Note that a second order polynomial fitting still works without twist it).

  Try the and see for yourself.

• Fitting with integral functions

  Hello

  I try to fit the data with full functions.  It is impossible to obtain analytical solutions of the integrations.

  Integration is integral [(T - abs [x]) f (x) dx, T, - T]

  Here, f (x) is one of the functions of autocorrelation for different model systems.

  Thank you

  Doogie

  Hi Doogie,

  We certainly have the integration and curve build VIs in LabVIEW. For example, you can find several kinds of system integrators in the mathematics > integration & differentiation palette. Also, if you use our design Simulation tools by & control, that built the integration as well. However, because you are dealing with an equation as opposed to sampled signals, I'd start by programming your equation in LabVIEW. Take a look at this forum thread that discusses this, and examples of code.

  Once you have programmed the equation and can generate an array of points for your stove, you might try to enter a function of integration as the "Integrate x (t) .vi" and then use a function as the "general polynomial Fit.vi" curve to generate an equation fitting for him. I would try getting started in this way. Please let me know if I address not the functionality that you are interested in.

  Best regards

• B Spline Fit Lockup

  Hello

  I've implemented the function B-Spline fit to find a curve of standardization. With specific sets of data, the program is suspended in the call from the library of NI_AALPro.lvlib:B - Spline Fit _nD .vi and ctrl alt del is the only way to escape. After you change the order of the polynomial fit or the number of control points he is still hindering on the data set.

  I'm under Labview 2009 with the complete development package, version 9.0f2.

  What is a user error? If not, does look like a bug in the routine curve? And nobody knows how to identify a problematic set of data before the interruption occurs?

  Attached is a sample of code with a data set that causes labview to lock up, so make sure that you have saved if you run!

  Thanks for the research!

  -Bill

  I looked more closely at your last 2 points of data and discovered that they have the same x value. By changing the last x don't value to the 6th decimal no hang up occur.

  Ben64

• Creation of period moving average trend line 50

  HI, im trying to set my curve in LabView and trying to create a 50 period moving average treadline as in excel.

  is it possible for me to do in LabView?

  I tried general polynomial Fit VI and a few other screw in unions, but failed to get anything close to the way I want

  any ideas? anyone?

  Charlie, there is a better VI called means"PtByPt". Look in the palette "Signal Processing > point-to-point > Prob and Stat > means. Add an advantage: this VI gives data valid for the first 50 points, although the average is not "development" or "stabilized" during early iterations. (Also, don't forget that primitives "delete table ' and 'Building the table' call memory, meaning Manager memory copies of great paintings and fast loop rates will result in a bottleneck of the CPU.) Using circular buffers is one way to alleviate this limitation.)

  

  64864050, try to adapt this code to meet your needs:

  

• algorithm to find the top of the parabola

  Use case: mower rejection of common-mode using a programmable potentiometer

  Problem: The performance of each circuit varies greatly and you are looking for best value (lowest CMRR) gives erroneous results. The performance seems to be relatively flat on some circuits, straight on others. Launching in the middle range of the potentiometer and moving upwards or downwards, I compare the measured value after the change of the potentiometer to the last measured value. By doing this I can get for the lowest CMR.

  Setup: entry wave sign 5V 60 Hz on both positive and negative of a differential ADC. The potentiometer is cut and reduces common-mode noise. Go away and the common-mode noise increases.

  Question: I would like to use adjustment curve to calculate the shape of the performance of the CMR. Take several steps (no more than 10 then I hope). Get the x y (x = 0 to 1023 trim adjustment potentiometers, Y = amplitude of the measured signal common-mode). Find the vertex.

  Is this possible and can someone point to an example.  I have not found one.

  A parable is a second order polynomial curve.  The Summit must be the peak value.  The general polynomial Fit.vi to maintain your data. The Coefficients of the polynomial outputs to calculate the location of the tip with a DAB of analytic geometry.

  Edit: Note that you may need to do checks to make sure that your data has not generated any curve as a parable.

  Lynn

• How to mount a polynomial if waveform to XY cluster is present

  Hello. I'm quite new to LabView and I'm getting a huge VI. It is an application of spectrometer. Somehow, I must add a polynomial fit to a graph XY of the final results. But I do not know how to manage cluster, how to separate x and Y of the points of data to make an adjustment, and then how to combine, to have additional conspiracy mounted on top of data points. Please take a look at the attached picture.

  You have any ideas, how could I do?

  Thank you!

  Well, your just combinaisonprincipale blisters with useless local variables and the race conditions, so I decided to not touch it, but just to show the General procedure. See if it fits your need.

  

• Polynomial to scatter

  Hi all

  I was wondering if there is a way to generate a polynomial fit to a diagram of dispersion as in excel. Data that I'm trying to adapt have several values of y for each value of x.

  Thank you

  Krish

  You must sort the data by X. Here's how it could be done. See if it works for you. (currently you try to adjust the data which zigzags in the plot area.)