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Questions tagged [curve-fitting]

Methods used to fit curves (as in linear or non-linear regression) to data.

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Scale and Translate a parabola to a golden distribution(which is also parabolic)

I have multiple image histograms(difference images) whose distribution is parabolic.I use least squares to do a quadratic fit .The questions is how do I scale and translate this parabola to a golden ...
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1answer
39 views

Estimate parameters of a normal knowing the density function

I have a matrix with 3 columns. The first column contains values of a variable $x_1 \in [-1,1]$. The second column contains values of a variable $x_2 \in [-1,1]$. The third column contains a variable $...
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39 views

Statistical significance of parameters in nonlinear model

I have historical data for mineral production in a specified region, from 1972 to 2014. I fitted the data to a model following a bell shape, in order to estimate the peak year and production. The ...
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1answer
33 views

How can I make a Kolmogorov-Smirnov test to check if my data distribution is exponential?

I made a histogram of my data, and the fitting line, but from some reason the fitting line doesn't fit to my graph. How can I make it fit to it? How can I check if my data distribution is exponential?...
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Uncertainty in calibration/curve-fitting parameters

Let me preface with saying I have an idea of a solution, but I am interested in other ones I am interested in the a way to quantify the uncertainty in a calibration/curve-fit parameter. For all ...
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24 views

Scaling and Transformation of histograms

Basically I have some histograms of images which I want to scale and transform so that if I apply a single threshold then I would get a constant alarm rate.How can I go about doing this.Below are 2 ...
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38 views

Matching a quadratic model to a linear model to give constant false alarm rate

I have a linear model which estimates the false alarm rate on different regions of an image on thresholding. Meaning the rate of false alarms is constant for all regions when a single threshold is ...
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1answer
40 views

How to fit a set of curves having some free and some shared parameters?

The problem I have a data set with 1 dependent and $N$ independent variables $x_1,\dots ,x_N$ (all real numbers), and need to fit a (nonlinear) function/curve $$ f_i(x_i; p_1,\dots ,p_{k_F}, r_1, \...
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22 views

Extend Best Line Fit methodology to a Grid

Sometimes, I'm provided with some data, a list of (x,y) points, and asked to determine a best-fit to some polynomial (or other function) that produces the inputs into the function that when chosen, ...
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1answer
27 views

How to extrapolate partial curve based on other complete curves?

I heat a room to a certain temperature. Then I let it cool over time. I measure the temperature at 6 intervals as it cools. I repeat this process for some other rooms. From this, I get a set of ...
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15 views

How to do curve fitting with data from measurements of experimental replicates (dose-response)?

Attached an image of a scatter plot based on sample data. I have tried searching the web but found only a video by Originlab doing concatenate fit. Tried looking for examples that use SPSS, Magicplot ...
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1answer
33 views

Get lower bounds and upper bounds of a curve

I have fit the wave data as below using Least Square optimization and used Root Mean square to calculate upper and lower bounds. I wanted to know is there any other alternative exists which gives a ...
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2answers
179 views

Fitting pmf of a scaled Poisson distribution and Python histogram plotting

I have a nuclei meanlife of $550\mu s$, for which I've taken the frequency(rate) to be $1/meanlife = 1818$. I then sampled randomly from a poisson distribution with that frequency, taking the ...
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2answers
55 views

Fitting curve to non-decreasing data

I have the below data. I want to fit a non-decreasing curve for this data. But, althouhg its grağh seems so regular, I couldn't find a suitable form of function. What kind of function may be suitable ...
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27 views

Working out a metric for the goodness of fit for 2D data in time

I have a dataset which I wish to optimise a fit for. The data might look something like I.e. orange is t=0, blue is t=1, and green is t=2. I wish to find a fit. I have a differential equation ...
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41 views

what is the best model that can be fitted onto a retention curve

I have a retention curve from activity data from customers which trends from 100% on day 1 down towards 0% over team in a curve. I need to fit a model to extrapolate this data past what data I have. ...
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25 views

Covariances and correlations in curve fitting

I have a set of data that I am trying to curve fit and I'm ultimately interested in the errors on my fit coefficients. I take my errors on each fit coefficient as the on-diagonal elements of the ...
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1answer
43 views

Approximate the data to a single curve

The question might be simple, but I am not able to find the answer. Hence I am asking here. I did search google but didn't get an answer. I have a continuous stream of data coming from an API in the ...
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1answer
50 views

Regression for curve fitting

For a curve generated from dataset points, split the curve into parts and obtain the best-fit degree of polynomial,coeffcients and the interval/range of the split through implementation in python.I am ...
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21 views

Area under the curve in smaller and uniform intervals?

I have 5 million individuals falling into 30 odd intervals, something like the below: 0: 9000 1-49: 8525 50-99: 7593 100-199: 7385 200-299: 4242 ... I would like to approximate the number of ...
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33 views

Confidence interval of fit parameter

First of all: I am quite new to statistics, so please don't tear me apart. ;-) I am currently trying to calculate a confidence interval for a fit of a curve to measured data points. I have done this ...
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1answer
42 views

Fitting a curve or raw transformation in a logistic regression

For my project, I am fitting a logistic regression to the some 'dummy' bank data. The head of the dataset looks like this ...
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1answer
47 views

method for predicting a curve

I have data on several curves. the data is of the form: curve_id x y and there are many x/y pairs for each curve and x is limited to some known range. overall, the curves look quite similar in ...
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71 views

How do I fit a cumulative Gaussian distribution in R? [closed]

I am trying to fit a cumulative Gaussian distribution function to my data, but I'm not sure how to do this. From what I understand, the fitting process tries to find the mean and standard deviation of ...
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1answer
21 views

Analyse variation between distribution curves according to factors

I have a set of continuous distributions representing the leaf area density found at different heights through a forest canopy. e.g. like that found in Whitehurst et al. (2013): For each of these ...
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25 views

How AAE is calculated for curve fitting and what does it's value indicate?

I have experimental results which are fitted to different equations, the fit is assessed by R^2 and AAE and I don't know how to interpret AAE values.
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1answer
309 views

Finding the appropriate polynomial fit in Python

Is there a function or library in Python to automatically compute the best polynomial fit for a set of data points? I am not really interested in the ML use case of generalizing to a set of new data, ...
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1answer
322 views

How to run a regression analysis in python on a nonlinear, strange dataset

I can't figure out what type of regression analysis or extrapolation technique to use in order to come up with an equation for the data I have plotted. For a school project, I've been testing diodes ...
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0answers
10 views

Definition of a 'design adaptive' fit?

When studying non-parametric regression, I've been told that local linear fitting is often better than local constant fitting at the job of estimating regression functions because local linear fitting ...
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1answer
55 views

What method can I use to produce a single curve from a number of curves?

I am looking for a good method to combine a set of curves into a single curve. Those curves have been produced by performing a measurement/testing n-number of times under similar conditions. What I ...
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0answers
34 views

model of two gaussion curves

How can I create in R a model that contains two Gaussian curves that describe that data I got. So I could get in the end the sigma and median of the Gaussian and calculate which datapoint belongs to ...
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1answer
29 views

Normalize Weights in fitting a curve

I am trying to fit a curve to set of data points. I have a set of weights that I want to assign each point while fitting. My question is that should i normalize the weights or use the weights as they ...
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2answers
38 views

Define prediction interval for a monthly sales pattern

The point of my analysis is to develop an alert system to detect when the sales of the current month are deviating significantly from the monthly forecast and guess whether the month is going to close ...
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1answer
74 views

Curve fitting in the presence of prior beliefs about the relationship between x and y

In the figure which follows each dot represents a game of a particular sport. The x-axis represents the home team's margin of victory, and so around the top-right we can see a game where a home team ...
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72 views

Fitting a logistic growth curve with an iterative formula in R

I'm trying to fit a logistic growth curve to specific countries GDP data using an equation, $P_{n+1} = rP_n(1-\frac {P_n}{k})$. (1) I've found constants $r$ and $k$ simply by finding a ...
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19 views

how to fit a curve on 20 pairs data [closed]

how to fit a curve on 20 pairs data ? (For instance a 4th polynomial to 20pairs datapoint) in python? And then how to add some deviation to them? for instance 0.5 deviation?
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1answer
81 views

Fitting a left-skewed curve to data [closed]

I have the following data for x and y-axis inputs. I am trying to fit a left skewed curve (i.e. long right tail) with a steep right peak to this data in R. I am not sure what curve equation to use (...
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comparing discrete and continuous measure performances

I am trying to estimate the value of the response/dependent variable based on the Age value. First, we used the defined age intervals to estimate the dependent variable and then we considered age as a ...
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1answer
158 views

How does Excel interpolate / imputate missing values in time-series when fitting a line to a plot?

I have a scatter plot in Excel (upper part of the screenshot) of time-series data. In-between the values that I plot (to the left), are some missings. I fit a (linear) line to those values and display ...
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76 views

Average of two fits vs fit of a combined data

Lets say I have data from two independent simulations. One of them look like this: The fitted curve is done by minimizing absolute difference between each data point and the curve. The fit ...
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25 views

Curve fitting testing basics questions

I'm learning all this stuff, so bear with me. A marketing professor in a university class, did the following: He wanted to do a projection from a very small data set of just 7 numbers. Using Excel ...
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1answer
63 views

What are some left skewed models for curve fitting?

I am working on some data on thermal performances on my organism for my thesis. I came across the Ricker Model which is a right skewed curve as shown below. How can I modify it to become a left ...
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1answer
35 views

cluster analysis in R

This is (a piece of) my data frame ...
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57 views

How can I find the k-nearest neighbors for a collection of linear time series data?

I need to figure out how to determine the nearest neighbors of an "optimal" line, as illustrated in a simplified figure, linked below. The blue, orange, green, and purple lines represent the best fit ...
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1answer
441 views

How to know if a parameter is statistically significant in a “curve_fit” estimation? [closed]

I use curve_fit from scipy to estimate parameter values from a specific function. ...
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104 views

Fitting Data to an Unknown Distribution

Consider a sample $x_1,\ldots,x_n \sim F$ from an unknown parametric distribution where $F$ is the cumulative distribution. We observe data in the form $F(x_1),\ldots,F(x_n)$. Stated differently, we ...
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254 views

Fitting a Multiple Gaussian Peaks to a Smooth Curve to Calculate Resolution in R

I used interpolation to fit a smooth curve to my data. I did this in order to visualize peak and valley regions. My goal is to calculate resolution (separation between peaks). I have peak to valley ...
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12 views

Deconvolution of 2 vectors (1 know + 1 unknown)

I am currently trying to deconvolute 2 vectors (a & b) from 1 (c). Actually, I have access to the recorded data of (a) & (c) but not (b). All are signal vs time with signal totally random. I ...
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1answer
102 views

How to deal with unstable estimates during curve fitting?

First of all, I understand this isn't a strictly statistical question, but I've seen other questions involving optim() here. Please feel free to suggest a better SE ...