Questions tagged [starting-values]

Many computational statistical problems (including some estimation problems, such as fitting GLMs) cannot be solved in a single calculation step - their algorithms must be iterated repeatedly until convergence. Such algorithms need starting-values at the beginning of the algorithm.

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Start function issues using nls

I want to statistically compare two curve fitting from two different dataset : pA3 et pE5. They both follow sigmoid curves (I do not use high enough concentration of pA3 to see the lower plateau). So ...
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21 views

Get initial parameters for growth models with nls whith non-common functions like “Ricker2” or “Richards” functions

I usually fit the most commonly known growth models using the FSA library and with the function selfStart. Now, I am trying to test some models with the Original Gompretz vbFuns("Ricker2") ...
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91 views

Box-Cox power transformation, adding or subtracting constants, and interval scales

I am trying to understand how the Box-Cox power transformation works. So I took one of my datasets and ran the powerTransform function of the "car" package (via R Commander) after having computed a ...
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23 views

using own data as starting parameters for modeling

I'm currently having a heated debate with coworkers on whether it's acceptable to use estimates derived directly from the data as starting parameters for modeling. For example, if I want to fit a ...
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149 views

Trouble fitting my data with non-linear Regression model

I have a dataset that contains tree height and diameter measurements among the tree stem. I tried to fit my data with GNLS in R, but I'm getting this "step halving factor reduced below minimum in NLS ...
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600 views

Initial conditions for nonlinear models using the nlsLM function

I have a data frame containing 70000 rows. For each row, I am trying to apply the nlsLM function (minpack.lm package) to find ...
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2k views

Specifying starting values/modes for K-modes Clustering

I have a very large data set with 9000 observations and 25 categorical variables, which I've transformed into binary data and preformed hierarchical clustering and K-modes clustering in R. ...
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1answer
870 views

Non linear regression - Von Bertalanffy Growth Function - Error: “singular gradient matrix at initial parameter estimates”

I am trying to estimate VBGF parameters K and Linf using non linear regression and nls(). First I used a classic approach where I estimate both parameters together as below with "alkdyr" being a ...
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45k views

Why is nls() giving me “singular gradient matrix at initial parameter estimates” errors?

I have some basic data on emission reductions and cost per car: ...
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1answer
2k views

MLE2 (in R): I can't find the right starting values

I am trying to fit several MLEs on a small dataset. I have managed to get it done for all my potential models except for this last one. This last one is actually the model that I expected to be the ...
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2answers
4k views

Exponential smoothing models backcasting and determining initial values python

I have made python code for exponential smoothing (ES) that takes in about 15 different cases including: Simple Exponential Smoothing (SES) Simple Seasonal models (both multiplicative and additive) ...
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5answers
23k views

How to choose initial values for nonlinear least squares fit

The question above says it all. Basically my question is for a generic fitting function (could be arbitrarily complicated) which will be nonlinear in the parameters I am trying to estimate, how does ...
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8k views

What are “starting values” in glm() function?

What are parameters start, etastart, mustart in the glm() function? I have been looking in ...