# Questions tagged [nonlinearity]

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### What should I do with RCS after finding non-linearity in a cox model

Hi I am conducting cox regression analysis. I found out with RCS macro on SAS that our variable 'systolic bp' has non-linearity issue. So, in this case how should I report the results? Our main ...
190 views

### Multiple linear regression homoscedasticity/linearity

My question is about the implications of the violation of homoscedasticity/linearity for multiple linear regression. I have tried to find the answer in multiple sources but could not figure it out. I ...
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166 views

### Splines, logistic regression and sample size considerations

I have around 500 observations with a binary outcome at 25% prevalence and will be building an internally validated prediction model. I want to use splines to model non linearity in my continuous ...
106 views

### What does it mean when dots on a residual vs fitted graph are clumped like a shotgun result? How do I fix it if it needs to be fixed?

Here's the code for these graphs ...
69 views

### Is there any approach to know the shape of nonlinear correlation between two variables?

I have read some of the existing non-linear correlation analyses such are Maximal Information Coefficient (MIC) and Distance Correlation, both of them don't tell us about how the correlation is shaped ...
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146 views

### Ramsey RESET Test

The Ramsey RESET test uses the fitted value of y to test nonlinearity, for example: $$y_i=x_i\beta+\epsilon$$ $$\hat{y_i}=x_ib$$ $$y_i=x_i\beta+\gamma\hat{y}^2_i+u_i$$ Test if $\gamma=0$ Why do ...
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22 views

### What is the optimal technique for determining statistical thresholds?

Relevant context: epidemiologists define an outbreak according to six defined stages (investigation, recognition, initiation, acceleration, deceleration, and preparation). From a local perspective, it ...
• 101
1 vote
331 views

### What is the definition of a non-linear estimator? I heard that ratio of estimators is non-linear

Why don't we consider nonlinear estimators for the parameters of linear regression models? says that LASSO is a non-linear estimator. I think LASSO has a solution via matrix multiplication. I don'...
1 vote
37 views

### If all computed features ( or components ) in Neural Network nodes are positive numbers , does using Relu meaningful?

I am trying to understand the following issue. The reason we use activation functions such as sigmoid,tanh or relu in neural networks is to obtain a nonlinear combination of input features ( x's). My ...
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1k views

### Modelling non-linearity for binary independent variables in logistic regression

I have fit a logistic regression where the response variable is binary - whether an interview candidate got the position or not - and the independent variables are a combination of continuous, ...
• 399
6k views

### A linear pattern occurs on my residual plot: what can I do?

I'm a bit stuck with a problem here and any kind of help would help a lot :) Just to give a clue about my data. I have 6 independant variables (IV) which are: $X_1$ = Population -within a block- $X_2$...
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64 views

### Variable relationship case: x1 is not correlated to y but x2 which is related to x1 is correlated to y

I would like to know what is the specific term given to this case, or how is this justified in technical words: x1 is not correlated to y but x2 which is correlated to x1 is correlated to y.
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### Exploring relation between x and y [duplicate]

While there are numerous methods in exploring relation between x and y upon receiving a new dataset. Yet it seems I can't find any conclusive guide as of the sequence of analysis, e.g. do correlation ...
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422 views

### Dataset with low and non-linearly correlated variables: suggestions on modelling strategies

I have a dataset with low and non-linearly correlated variables and I am interested in assessing the relations between the Independent Variable (IV) and Dependent Variable (DV), however I am not able ...
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1 vote
3k views

### Checking linearity in logistic regression

I am conducting logistic regression, and I am a bit confused about the linearity check? I have 18 independent variables, among them, 13 are continuous, and 5 are categorical variables. In this ...
758 views

### How to interpret p values of a non-linear covariate using pspline in a coxph model

I tested the assumptions for Cox proportional hazards model on my time-to-event data. I found that the assumption of linearity between independent variables and model residuals is violated. After some ...
1 vote
184 views

### Does this scatter plot suggest non-linearity?

As part of assumption testing for ordinary least squares (OLS), I am examining the linearity between the variables in my model. I'm using scatterplots between the independent variables (IVs) and ...
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1 vote
171 views

### Linear and nonlinear feature extraction methods

I far what i understand, the assumptions for PCA is that data should be linear. What does that imply? let say if i have a data of 1000*100. So all independent variables should be linearly separable ...
2k views

1 vote
82 views

### Left censored dependent variable in SEM

I'm working on a structural equation model in Amos. I have two independent variables, 5 mediators and a left censored dependent variable. The dependent variable is ...
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