# Questions tagged [curve-fitting]

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

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### What's the use of curve fitting for a function $y = f(x)$, if I can reduce it to a linear regression?

Suppose I have data points $(x_i,y_i)$, say $N$ points. I know they are supposed to fit the curve $y = f(x)$. Are there techniques more advanced than linear regression, for such cases to fit the curve?...
1 vote
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### Classifying multivariate data as gaussian, non-gaussian, or a mixture of gaussians?

It's for the following use case: I have a set of "detects" of a group of individual targets (mostly stationary) that I wish to cluster or segment such that each cluster (group of detects) ...
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### Fitting a well-specified 1D function of time to 3D spatial and spatially correlated data

I have acquired experimental data that can be considered to be a scalar field in physical three-dimensional space, $(x,y,z)$ that I have observed over time, measured on an equally spaced regular grid. ...
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### Forecasting two dependent count variables using single independent variable (Time)

I'm stuck with a modeling problem without any results in my org. The model first should be developed based on time (in M or W) in x axis and booking counts across y axis. Next it has to be identified ...
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### Logistic regression - Confidence interval for x axis

My question is very similar to the post Confidence interval for x-values given a probability in a logistic regression where ultimately no answer was given. I have also posted a similar version on the ...
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### What is the best method for fitting a curve that has the dependent variable on both sides of the equation?

I am trying to fit a curve to a set of measured data. Similar studies have been done, and the resulting curve fit is usually of the following form. \frac{1}{\sqrt{Y}}=a \log{\left(X \sqrt{Y}\right)}-...
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### Confidence bounds for coefficients of a fit of data set obtained with another fit

I fitted an equation to a set of data points. Then I substracted the fit previously obtained to another set of data points. After that, I fitted another equation to this new data (result of the ...
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### How do I calculate the 95% confidence interval of a curve that depends on many parameters?

Assuming I have a curve fit that depends on 4 parameters. How would I compute the 95% confidence interval if I had many variations of this curve fit (many combinations of samples of these 4 parameters)...
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### Logistic 3 Parameter (3pl) prediction model calculation

I´m currently working on a prediction model using Logistic 3P fit with JMP. I´m obtaining very good curves using the calculated fit model. The model is the following: y= c/{1+exp[a*(x-b)]} Where a is ...
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### Predictions based on data with correlations within and between multiple sets of time series

I'm looking for a model to learn relationships within and between a set of partially observed time series in order to generate predictions for any timepoint in any of the set of time series. More ...
1 vote
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### How to calculate uncertanty of extremal point of fitted quadratic polynom?

I am doing some fitting in python, that is: ...
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### Pick minimum value based on MSE and point

I am attempting to automate some processes at work. Im familiar with statisical methods such as GLM, ANOVAs, Basic OLS, etc. But I am unsure of methods which I can use for this. problem statement: ...
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### Peak fitting using unknown formula

I was interested in determining what "full employment" meant in the US by looking at the various peaks in unemployment over time and trying to fit a model through it. My assumption based on ...
1 vote
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### Growth curve analysis in R - time variable as a polynomial

I have narrowed down some specific questions and was advised that it's more appropriate to post them here than on stackoverflow I'm building a growth curve model using lmer in R and I'm unsure about ...
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1 vote
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### Growth curve modeling using lmer - how is it different from mixed effects regression?

EDIT: I'm realising time cannot be a random effect, is that right? Where does it fit with other fixed effects? Can time be a polynomial? I am trying to set up a growth curve analysis using lmer, I ...
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1 vote
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### Using curve_fit for Non-Linear, Multi-Variate Models [Python] [closed]

Warning: ML Noob. I have a 3D dataset (data at the bottom) with 2 feature variables and 1 target variable. Polynomial Regression produced unsatisfactory results and it seems that the relationship of ...
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### Unsupervised classification of objects based on relationships

I have size measurements of 1000 objects, measured over time. I would like to classify the objects based on the response of their size to time using unsupervised classification. For example, the size ...
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### How does the TI-84 calculate the best fit for a logistic model?

Back in High School I remember the TI-84 calculator allowing the user to enter a few data points and then select from a list of options to find an equation that best fit the data points. One of these ...
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### Combining data from multiple studies - best approach?

I'm looking at an old paper on the incidence of HPV infection by age cohorts. The authors present a plot of estimates from many different studies around Europe which looks like this - note the authors ...
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### Recovering samples from a density estimation with an additional prior on the samples. Used for Gibbs sampling

Abstract Idea: Given a noisy measured density ($d_j$ at position $p_j$) and a density model, sample from the model parameters under the following stochastic model: Stochastic Model: Prior for model ...
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1 vote
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### Describing / fitting a highly skewed distribution

I've got a data set of 84,529 entries, each entry referring to the number of times a particular entry is cited in a database. This set is extremely skewed, ranging from entries with 0 citations to one ...
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### How to fit joint models for longitudinal and binary (outcome) data?

Joint Models are mainly viewed in the literature within the context of longitudinal and time-to-event data. For this reason R packages as JMBayes were built to fit these kind of models. Nonetheless I ...
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### How to predict single y target based on several X values? [duplicate]

I try to predict the result of an personality type test based on how people answered. My sample consists of the answers which range from 1 (strongly disagree) to 7 (strongly agree). Six answers lead ...
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### Fitting Several Linear Regressions at Once

Suppose I have n stocks. X_1 ... X_n. In turn I want to predict the returns Y_1 ... Y_100 over some horizon t. Ultimately ...
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### Fitting a distribution to my data, and estimating future transactions

Assuming that I have a list of transactions generated by an unknown process. After fitting a distribution to my data I wish to report the projected sum of n transactions - assuming that it's generated ...
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### Fit a Gaussian function (not a Gaussian distribution) to data

I am trying to train a Gaussian function. NOTE: Since we're on a Q&A site with one of its focuses being Statistics, it is worth emphasizing that not all Gaussian functions are normal ...
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