Fitting Definition and 224 Threads

Hi. Has anybody here any experience with SciPy? I'm trying to get SciPy to adjust a gaussian function to some data. For more details its the photopeak of Co60. This is what I do: import numpy as np from scipy.optimize import curve_fit # counts is a numpy array which...

Homework Statement So I've done an experiment by scanning over a range of angle and measuring the intensity of X-Rays. There are peaks where I have X-Ray diffraction occurring and in order to do analysis I need to identify the values of angle and an error (as in the plus/minus) on this value...

I am doing an experiment that generates data in three 1-hour-blocks. Each block has a different number and timing for acquisitions. (The first hour is more frequent and numerous, while the last hour is only 6 acquisitions) The reason for breaking it up into 3 hours is to give the subjects a...

I plotted a graph on Origin software and need to do curve fitting to get accurate results. From my understanding, I need to provide a function for the fitting. So how do I derive the function? I am actually provided with the function I(x)=I0-I1cos(x-x0) and this function will fit the lowest...

I have a set of data points that I must fit to an inverse function like this: y(x) = a/(x+b) + c My problem is that least-squares fitting using this equation is extremely unstable and heavily dependent on initial guess. No matter how accurate parameters I start with, the algorithm often goes...

This isn't a precise homework question, but this seemed like the most reasonable place to post. If not, please feel free to move it. I have a large set of data points that should fit to a known equation (the Drude-Smith model for conductivity) The equation the data should fit to is: σ(ω) =...

It has been a very long time since I have done any calc or hard math, I hope this question is in the right place. I have a HUGE number, that is random and big. What do I need to study/look at to create a formula that will generate just it?

Hey everyone, I'm hoping I can get some input on this. As some of you may recall, I'm currently in an internship at Fermilab, and I've hit a snag in plotting my data. I'm measuring the intensity of the NuMI neutrino beam at multiple different points to look for discrepancies in the measured...

PF, I work as a researcher at my undergraduate institution. I have to give a presentation in a week and this question always gets me. What does learning the properties of these SNRs contribute to the overall body of knowledge? What does the scientific community gain from this knowledge...

I have several questions about the process of determining the value of cosmological parameters by LMS fitting tunctions of the form z = f(DL) (where DL is the luminosity distance to astronomical data points), for example, as shown in the following diagram: The five cosmological parameters I am...

Hi all, Does anyone know of a quick release fitting that can replace a screw thread? I'm thinking along the lines of a bayonet fitting but any other ideas would be great. Looking to put pieces of wood sticking out perpendicularly from a wooden wall (railway sleepers) to act as supports for...

I have a question about the logistic fit they used on this paper: http://online.liebertpub.com/doi/pdf/10.1089/cmb.2005.12.1047. Its PDF page 5, or journal page 1051. They define all the variables and then say x0 and b define the shape of the model. If I am fitting 30 cycles of PCR data how am I...

Hey, sorry if this is not the right section to post in, the topic is a bit ambiguous. I've generated a set of coordinate points for the orbit of Mercury (3d cartesian) and now I want to fit an ellipse through it so I can get an accurate estimate of the location of the perihelion. I am using...

I have one dimensional binned data that has a peak to which I need to fit a distribution, such as Gaussian or Lorentzian, that is described with four parameters, height, width, centroid position and the background. The problem is that the counts per bin are low and the peak is only 5-6 bins wide...

Dear users, I deal with following problem. I've got a data of Intenzity of chemiluminezcence as a function of temperature. The data should be fitted by following equation: I found that in origin one can fit also data with integral function, with fittin parameters P, A, i, E. The beta and...

I have some (x,y) data with x in the range of 1e10 and 1e13, y is between 0 and 1. I am fitting this data using several theoretical models to gain an understanding of underlying mechanisms (by which model fits best). Using NonlinearModelFit in Mathematica, I get memory failures and cannot...

Hi Folks, I have a curve that varies sinusoidally calculated from a numerical program as attached "Trace.png". I would like to fit this amplitude modulation expression to it. f(t)=A[1+B \cos(\omega_1 t+ \phi)] \cos(\omega_2 t+ \theta) I managed to adjust the parameters manually to get a very...

Hy, I wonder which is the good solution for this problem: Nonlinear least square problem: function: y = x / (a + b.x) linearization: 1/y = a/x + b substitution: v = 1/y , u = 1/x >> model v = b + a.u What we did in school: x = [1 2 4 7]; y = [2 1 0.4 0.1]; v=1./y; u=1./x; n = length(x)...

Is there a software(preferably free) that can fit data into a 4 parameter equation? like the generalised logistic function

Hello, my problem is the following: A lasers gives out a bunch of data points which are reflected off a metal surface and recorded by a camera attached to the side of the laser. The image the camera receives is however distorted. In order to calibrate the camera I need to find a function...

Hello! :-) I' have a problem... I fitted experimental data with a second order exponential theoretical curve: y = A1*exp(-x/t1)+ A2*exp(-x/t2) + y0 and I have these data for 4 repetitions of the same experiment: first time: Reduced Chi-Sqr = 6,81066E-4 Adj. R-Square = 0,41005...

I have a list of scores between 0 and 1 generated by an information retrieval system - 1 being very relevant and 0 being completely non-relevant. I do not know whether the scores correspond to relevant or non-relevant items or not but I do know that the distribution of scores is generated by a...

I have a set of scored items with the scores in the interval [0,1]. Roughly speaking the distribution of scores is about 50% equal to 0 and then sloping steeply downward all the way toward one or near to one. I want to fit this data to a distribution and use that down the road in some...

I am looking for pedagogical guides to fitting rotation curves with MOdified Newtonian Gravity. I want to study how to fit the luminosity data as well as the kinematic data. I have studied some published papers on MOND fits(Sanders, Mcgaugh, blok etc). But, they are not sufficiently elaborate...

Hello I am working with fluorescence correlation spectroscopy. I want to fit the correlation function on Igor pro. Does anyone know how to fit the correlation function with Igor? I am willing to pay for the help.

I have several data points with error bars, and these error bars are different sizes for each of the data points. I'd like to fit a model function to them which has non-linear parameters, and be able to get error bars on the model parameters, ie. if my model is something like f(x) = A +...

Hello, So I was hoping to get some help implementing a nonlinear least squares fitting algorithm. Technically this is an extension of my previous thread, however the problem I am having now is correctly computing the algorithm So the problem definition is this: Given two sets of n 3D points...

Dear All, I would like to do an exponential function least-squares fitting, but having two or more exponents. For example the function looks like this: y (x) = A \exp (-x/a) + B \exp (-x/b) where A, a, B and b are the least-squares fitted parameters. My question is how to obtain the...

Hi, I wonder if someone could give me some guidance on this problem please. I'm not a mathematician and I'm not even sure what the title of this problem should be - curve fitting, regression, function minimization? It started with something fairly simple, least squares fitting with 3...

Homework Statement Determine the values of Sellmeier's coefficients (S and λ0) using the least-squares method and Sellmeier's dispersion equation: n2=1+Sλ2/(λ2-λ02)Homework Equations n2=1+Sλ2/(λ2-λ02) The Attempt at a Solution I understand how to use the least-squares method with a simple...

Hi! I'm doing a project with sound, and exploring modulation. I got stuck on an intermediate step ... and can't solve a simple algebra problem. I have a wave, which I know the envelope is a perfect sine wave, and fits the following three equations: A * cos( ph1 ) = knownSlope1 A *...

Hi, I need some directions to target a problem that is bothering me quite a lot, even some links or small explanation if possible, thank you in advance! I have a huge dataset Ω (unknown) of experimental values {e_i} that should approximate (with noise both in the value and in the...

Hello, I'm in need of someone to show me how to fit a bacterial growth curve to data in Prism, preferably using the Gompertz function. I also need someone to show me how to assess the goodness of this fit. I have many different growth curves and I need to compare the parameters. Hopefully...

If I was given some n(very large) points, and if I want to fit a curve circularly, I think I should go for least squares method. What is the optimal way to do it? can someone explain me clearly how to proceed using least squares method? I don't how to proceed. But I know I should do least...

I have a group of 8 3-D points which all sit on an arbitrary plane (The points were generated by projecting the corners of a axis aligned cube, box, onto the plane) I wish to group all the points in a rectangle with the smallest surface area - so a tight fit rectangle. What I am doing at...

Hey everybody I've got a question for the programming savvy. I'm generating data which can generally be described by.. f(x,y) = Ʃn(an * xn)*Ʃn(bn * yn) Basically what I'm looking at is a data set which shows a surface which looks like about 1/4th of a wonky bowl. My trouble is...

For my 3rd year project, I have a set of data which is the variation within an interference pattern. The outcome has clear sine curve properties (Alternating peaks and troughs of intensity) but the positions aren't regular (i.e. the peak-to-peak distance between peak1 and peak2 is larger than...

If I construct a curve such start from point A0, A3, to point A6 where A1-A2 and A4-A5 are control points, is called a Bezier curve. What is it called by and what its equation if I construct and fit a curve start from point A0 > A1 > A2 > A3 > A4 > A5 > A6 such as below image?

Homework Statement Just wondering if my output seems wrong. The interpolating polynomial looks like it's way off, though I've looked over my code many times and it seems right (?). [FONT="Courier New"]clc clear all format long x1=[1:1/10:4]; y1=zeros(1,length(x1))...

Here is the question: Here is a link to the question: Write a function for the polynomial that fits the following description.? - Yahoo! Answers I have posted a link there to this topic so the OP can find my response.

I model arterial baroreflex data that I have collected in humans using the Kent equation which is: y=p1/(1+exp((x-p3)*p2))+p4; where Y=heart rate, X= estimated carotid sinus pressure, p1=range of Y, p2=slope coeff, p3=centerpoint on X, p4 = minimum Y. I use Sigma Plot to do a best fit line...

I encounter a problem on the fitting ability of a special class of multi-variable polynomials. To be specific, I need find whether a special class of multi-variable polynomials, denoted by p(m), where m is the number of variables, can universally and exactly fit all member in another special...

Homework Statement Find all the primes p and q such that p^2-p-1=q^3 The Attempt at a Solution Trying out the first prime number 2, it is clear that p>q and that the difference is larger than 1. Then when factorizing it p^2-p=q^3+1 \Rightarrow p(p-1)=(q+1)(q^2-q+1), I get that p must...

Hello, I didn't know where else to post this so here it goes ... I have collected data from a pulsed NMR experiment to calculate the value of the spin-lattice relaxation time (T1). Now I'm asked to fit the data using a function of the form V(t) = V_0*(1 - 2*exp(-t/T1)). But I'm not really...

Hello, I would like to ask you some questions. 1) I've a closed curve (for example an ellipse, which may represent the contour of an object) represented by the set of its (known) points. I need to find the equation of that curve to pass through all and every point (exact fit). I think that...

Hello, I am currently doing a project and have ran into a problem. I have a structural fitting (clamp-on tee) that fits around a fixed structure. I am trying to fit an aluminum pipe into it, but the pipe's outer diameter is much smaller than the clamp-on fitting. I'm attach 2 images that show...

Hi, I m unsure whether or not this should perhaps be in the homework forum, however one might say this is more of a technical issue. I recently conducted an experiment for a report I intend to write up promptly, and I wanted to find the best fitting curve for these values. I tested how different...

I am trying to fit a cosine function to two points knowing that the first is an inflection point (e.g. a trough) and also knowing the gradient at the second. I have a gut feeling this has a unique solution it just needs the right identities and massaging but as of yet I haven't found the way...

I have a set of data points \{\{x_1, y_1\}, \{x_2, y_2\} ... \} each with an uncertainty \{\{dx_1, dy_1,\}, \{dx_2, dy_2\} ...\}. Is there any way of fitting a nonlinear model to the data that incorporates the uncertainties on both x and y? I know that you can use the Weights command to...

Can you fit data that is imported into Mathematica 8? I am just using the Import command, and I cannot figure out how to work with this data. I would really like to fit my curve. This is the code I used to import the data: Import[datafile.xlsx"]