# Tagged Questions

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

32 views

### Fit a Gaussian to data with R with optim and nls

I want to fit a Gaussian to the following data: ...
32 views

### Likelihood between two functions

I have a function $f(x)$ describing a physical process, and a function $g(x)$ that tries to approximate it. I can clearly see by eye when the two functions are close enough, but I would like a ...
222 views

### Fitting a smoothed curve to a noisy data

I have a variable with sales data over time. It is very noisy at a disaggregate level but if you look at it as a whole, you can see a smoothing curve that follows a polynomial pattern. Is there a way ...
12 views

### Fit tail to monotonically decreasing data

I am trying to fit several distributions to monotonically decreasing data, and pick the one that fit the best based on several criteria, e.g. mle estimate. I am able to do this by fitting a curve to ...
30 views

### Construct function from integral values

From measurements (only) the values $a_i =\int_{x_i}^{x_{i+1}} f(x) dx$ for some sequence of (equispaced) $x_i$ are known about a non-negative function $f$. What would be techniques to find a ...
8 views

### Combining the results of 4 fits performed on 4 different dataset

I have 4 dataset which are independent measurement of the same physical quantity. I have fitted each dataset with a certain model, as a result of the fit I estimated one parameter with its uncertaity (...
6 views

### How to take dataset uncertainty into account in distribution fitting?

If we have a dataset like x=(3,4,2,1,4,...,5), we have classic methods (method of moments, maximum likelihood method, etc) to fit a distribution. However, in certain real life cases, we can have ...
42 views

### 4th parameter of Boltzmann sigmoid must be greater than .9 in R

I'm trying to fit a 4 parameter boltzmann sigmoid and get an error: "Error in nls(y ~ a0 + (a1 - a0)/(1 + exp((a2 - x)/a3)), start = list(a0 = max(y), : singular gradient" I have figured out that ...
111 views

### Is there a formula for an s-shaped curve with domain and range [0,1]

Basically I want to convert similarity measures into weights which are used as predictors. The similarities will be on [0,1], and I will restrict the weights to also be on [0,1]. I'd like a ...
45 views

### Polynomial fit based on the addition of two least squares regressions

I'm wondering if there is a way to retrieve analytically the coefficient for a polynomial fit, based on a least-squares regression coming from two independent sources. Let me explain the context for ...
31 views

### Fit a curve to data with positive and negative peaks

I have some data from a finite element electromagnetic simulation, and I'd like to fit a curve to it (to allow me to scale the data without numerical artefacts). It goes to zero at plus/minus infinity ...
28 views

### How to detect the inflection point or the change point in a Q-Q plot?

Following are two QQplot. Both of them has an inflection point, which can be found easily by human eyes. However, I'm not sure whether there is a robust statistics way to find it.. Does anyone have ...
58 views

### How to improve a bad long-term forecasting of time series in common case

I have two time series $d_t(t)$, $d_c(t)$, where I'm modelling charge as a function of time. Lengths of time series, $N$ are equal to $101$ data points. For the $d_t(t)$ (test sample, short-term) the ...
13 views

### Powerlaw fitting with zeroes. Is this not the case?

As a result of a computation process which I cannot describe due to lack of time, I have obtained two datasets that I will simply call X and ...
15 views

### How to aggregate many simulation runs for curve-fitting?

I have results from about 200 runs of a simulation model. The results contain a stochastic response variable which I want to approximate with a curve-fitting approach. So far, I have opted for ...