Questions tagged [nonlinear]

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48 views

Can I use *any* activation function in my Neural network as long as it is non-linear?

I am currently learning about Neural networks and am finding it hard to comprehend the reason why activation functions such as ReLU or sigmoid are favored. In general, I understand the need for the ...
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0answers
8 views

Specifying interactions in nonlinear growth curve models

I have a nonlinear growth curve model with Time and Time^2 as well as one time-varying predictor (level 2) and one time-invariant variable (level1). I want to test interaction effects. Normally I ...
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0answers
13 views

Nonlinear relationship in logistic regression [duplicate]

I have a binary dependent variable (infection + or -) and both continuous and categorical independent variables. One continuous independent variable (BMI) seems to be nonlinear in that the lowest and ...
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0answers
8 views

Options for nonparametric preference ranking models

What are some options for nonparametric ranking models with a probabilistic interpretation? I'm basically looking for a nonlinear/nonparametric version of a rank ordered logit model. I'm aware of ...
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0answers
7 views

Testing cubic moderation of linear effects

I’m trying to test cubic moderation of linear effects and plot Johnson-Neyman regions of significance (or something similar that would tell me the time cubic values at which the effect becomes ...
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0answers
18 views

Pairwise Contrast on relative change emmeans package

So I have it a Generalized Linear Mixed Model and am looking to do contrasts. However, in this case, the biochemically relevant contrast is not a simple difference of differences. It is the difference ...
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0answers
32 views

Need help: nested fixed effects in nlme()

I have two fixed effects in a nonlinear mixed effect model. One is nested in the other, as the case here: "Specie" is nested in 'category'. ...
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1answer
46 views

How to simulate non-linear regression model with splines?

I want to simulate a non linear regression model of the type $$y_i = 1 + x_i + bs(x_i)+ e_i,$$ $i=1,...,1000$, where $bs(x_i)$ is a b-spline. I have tried to use the ...
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0answers
53 views

Evaluation of variance components - mixed models

How can I evaluate if the variance components of a nonlinear mixed model make sense (assuming or not assuming treatments factor)? For instance, if I am assuming an unstructured variance-covariance ...
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0answers
23 views

Modeling approach to showing a parabolic effect is greater than that expected by scale boundaries

I have conducted an experiment where raters rate different nations on a DV. Each observation is a different nation. I calculated a mean and SD of the DV for each nation. The data we are working with ...
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1answer
33 views

Non-linear dimensionality reduction for detecting coordinate systems [closed]

I am trying to find a way to automatically find the appropriate coordinate system for a physical problem. For example, in the case of a simple pendulum, polar coordinates are the most appropriate ...
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0answers
25 views

Nonlinear fit in R only works with tightly restricting parameter bounds [duplicate]

I have a reproducible example here with an attempt to use nls to fit a nonlinear function: y = ax/(b+x) + c Even when I set the starting values to be a good, ...
2
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1answer
65 views

When to use non-parametric regression such as kernel, generalized additive model, spline, and polynomial?

I understand that kernel regression is a form of non-linear/non-parametric regression. However, I know you can also use generalized additive models for non-linear regression, as well as polynomials ...
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0answers
21 views

Nonlinear data to use in multiple linear regression?

I am supposed to be running a multiple linear regressions to test my hypotheses. However, when first testing the assumptions that should be met before performing a linear regression, it turns out my ...
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0answers
22 views

non-linear tikhonov/ridge regularization?

For traditional ridge regression, the loss function is $loss\_function = ||A\mathbf{x}-\mathbf{b}||_2^2 + ||\Gamma\mathbf{x}||_2^2$ https://en.wikipedia.org/wiki/Tikhonov_regularization Is there a ...
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1answer
34 views

Can VARMA handle non-linear data?

I know that traditional ARIMA models cannot handle non-linear data but I was unable to find any place where it states whether if VARMA can handle non-linear data or only linear. Please clarify this ...
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0answers
20 views

Comparing two groups (nested) and differences between multiple dependent variables (nominal and continuous)

What is the best method to compare two groups in this situation? For example, lets say I want to compare and find differences between men and women. The independent variables can be nominal (own a car,...
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0answers
11 views

Primal solution exists but dual does not

I am working on the follwoing nonlinear model. Min z=10(1-$\exp$(−3x) ) subject to: x $\leq$ 3 When I solve this problem on LINGO, I got the message "dual solution does not exist but primal ...
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0answers
17 views

Estimate the Beta Coefficients, and then find an algorithm

Referring to the photo, I need to report my beta coefficients as functions of observed Xi and Yi. I tried to reduce by taking the log of both sides but It seems I can't reduce this model because it is ...
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52 views
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1answer
32 views

Estimation of model with non linear dependent variable

I am trying to verify whether two variables are linked by a relation of the type: |y|=ax or y^2=ax. What could be the right statistical procedure to verify whether the above relations are correct and ...
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11 views

Non-linear parameter multinomial choice model

I am trying to develop a multinomial logit model with nonlinear parameter of the following form Here, dj represent a vector of proxy size variables for zone j and d is a corresponding vector ...
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1answer
72 views

SVM non-linear decision function using hyperline

Suppose that we have a toy classification problem X -> y in 2D. In scikit learn, I solve this question with X = np.array([[2, 1], [3,1], [3, 0], [4, 0], [5, -1]]) y = np.array([0, 1, 1, 1, 0]) from ...
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23 views

Variance of the mean in case of a quadratic trend

Please allow me to use Python code to put my question across. Suppose we want to model a variable using either a linear or a quadratic trend: ...
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0answers
174 views

cumulative distribution function for non-normal distribution

From this article, I read that the author drew four versions of CDFs each plotted in different distributions (all four plots come from the same sample data) From these four plots, the author chooses ...
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1answer
33 views

accounting for age effects: two age groups and within-group age differences

I am analyzing data from a study with two groups of about 25 healthy participants each, one young (mean age ~25 [~18-~30] years) and one older (mean age 59 [45-75] years). The study was set up mainly ...
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0answers
10 views

Usage of correlated (non-linear correlation) variables in an experiment and standardisation of variables values

The setting (see the dataset at the end of the question) The setting of the problem is this: I ask many multiple choice questions; only 1 out of the 3 available answers is correct; I ask the same ...
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0answers
87 views

Should I standardize my variable for regression before nonlinear feature transformation?

I would like to fit a non-linear model by doing nonlinear feature transformation first (e.g. exp, log) and then using linear regression (or regularized linear regression). However, I am stuck at ...
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2answers
50 views

Would machine learning techniques help if the linear and nonlinear relationships is so weak?

I have a cross sectional data set at hand contains four predictors to predict one outcome, I employed bivariate analyses to check whether the relationship between the dependent and independent ...
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0answers
12 views

High error value when estimating model parameters

I have a non linear system of ODEs and to estimate 4 of the model parameters I am using Matlab fmincon by minimising the sum of squared errors (SSE). I have only 5 ...
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1answer
78 views

Conterfactual estimation in machine learning model

There are various techniques to build counterfactual estimations of certain variables for linear models in observational studies. Some of those are based on comparing the change in the predicted ...
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1answer
102 views

How can I plot relationship between two variables with the constraint of initiating the S-shaped curve from (0,0) as depicted in the example below?

I don't want to run logistic regression or any such regression model. I have 8 to 10 pairs of data points and want to analyze the logistic growth model by fitting any function-generating S-shaped ...
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1answer
209 views

Neural network for predicting a non-linear function

I want to build a neural network to predict $f(x)=\exp(-x)$ for every $x$ in the interval $(0, 5)$. I randomly generated the training set uniformly in the given interval with 500K training examples, ...
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0answers
80 views

Can I statistically describe a single case/outlier vs. a distribution?

I have a dataset consisting of body weight and corresponding age for a bunch of healthy subjects (grey triangles below). I fit a nonlinear function to this data and graphed a 95% prediction interval. ...
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0answers
279 views

Using UMAP or other non-linear dimension reduction techniques on response variables prior to learning?

Background Suppose you have a training set where the response measurements are some $N$-dimensional vectors of related measurements - in my specific case, they happen to be cell viability scores for ...
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1answer
285 views

Which features should I choose to create polynomial features?

Sometimes we want to use some features in our original dataset to create polynomial features in order to add non-linearity to our model. The question is how to choose those features? Do we choose ...
2
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1answer
227 views

What is the difference betwen a time non-homogenous Markov Chain and a non-linear Markov Chain? Example

A time non-homogenous Markov Chain is one in which the transition probabilities are not constant over time. A non-linear Markov Chain is a model that is not linear in parameters and satisfies the ...
1
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1answer
137 views

How to test for overfitting in a TAR model in R?

I want to fit a threshold autoregressive model, and I'm using the tar package in R. For ARIMA models, I could check if a model was overfit by looking at the values of standard errors as compared to ...
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2answers
218 views

What is an appropriate transformation of an age variable when used as a predictor of athletic performance?

My question concerns using non-linear transformations on linear variables in regression, particularly where you believe the predictive weight might peak at some central value of the linear predictor. ...
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0answers
20 views

Linear Unconditional X-Y, Non-Linear Conditional X-Y

Intuitively, I can imagine that an unconditional (i.e., unadjusted for any covariates) Y~X relation can present as a linear relation, whereas a conditional Y~X|Z relation can present as a non-linear ...
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0answers
39 views

Exploratory factor analysis of a non-normally distributed data set with probable multicollinearity problems

I am trying to develop a scale measuring employee satisfaction regarding organizational support using spss. Most of my variables are positively skewed which should not be a problem in EFA as long as ...
1
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1answer
156 views

Fitting power model to data with zeros

I want to fit a power model to some data. The model is of the form y = ax^b. I can take one of two approaches: 1) I can take logs to linearize the model, and use linear regression to find values for ...
0
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1answer
227 views

Including error dependent on output in Gaussian Process Regression

I have a set of experimental data that I am trying to fit using Gaussian process regression (GPR) using Python's sklearn package. The only problem is that my data has an experimental standard ...
0
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1answer
450 views

R lmer, 3 time point longitudinal data, non linear, messy residual help!

I am new to mixed models so please go easy on me! I am attempting to longitudinally model a normally distributed continuous outcome with values in my dataset from -30-10. I have data collected at 1, ...
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1answer
93 views

upper confidence bound of a non-linear model seems wrong (predictNLS)

I have the following data and R-script: ...
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0answers
55 views

Tests to check a non-linear relationship?

I have a non-linear relationship between two variable (tested using a linear and square term). Are there any tests that can provide validation for the non-linear relationship? I have tested Lind-...
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0answers
54 views

Relevance of residual normally distributed residuals in nonlinear regression

I have a mathematical equation, based on physics, that requires estimating several parameters via nonlinear regression. I have conducted such nonlinear regression estimation with a dataset of 1100 ...
1
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0answers
260 views

Price Elasticity Estimation with a non-linear price schedule

How do I estimate price elasticity in a non-linear price setting? Non-linear prices are seen in utilities (electricity, water etc.) where the price per unit is determined by quantity purchased. So a ...
4
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1answer
3k views

Algorithms to model non-linear relationship between two vectors

I want to build a model that describes a curve that fits the data shown in the scatterplot. I thought it would be straight forward using sklearn. But the choice and application of the different ...
2
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2answers
559 views

Cosine-Similarity vs non-linear measures

In NLP, people often use cosine similarity to measure how close two vector spaces are to each other. However, we know that cosine-similarity is the same thing as Pearson correlation, for centered ...