# Questions tagged [regression-strategies]

Regression Modeling Strategies

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### Logistic Regression with (Normal) Distributions for Independent Variables

Consider the logistic regression where $Y_i \in {0,1}$ are dependent variable observations and $X_i \in \mathbb{R}$ are the independent variables. However we do not observe the $X_i$ themselves. ...
293 views

### Determine rate of change in dissimilarity (distance)?

I have repeated measures plant abundance data for 36 forest plots, across 80 years involving 50+ species of trees. The data are structured as: Columns = ...
282 views

### Boruta Algorithm for Logistic Regression?

Is it okay to use a Boruta algorithm to select features for a logistic regression? I read several sources, including the source package as well as this site explaining what Boruta does. My ...
2k views

### How to find marginal effect of restricted cubic spline

I'm trying to figure out how to find the marginal effect of an interaction term from a restricted cubic spline in a non-linear model. The post Nonlinear effect in an interaction term is a good start ...
94 views

### OLR with rms: proportional odds assumption

I am fitting an ordinal logistic regression model with rms package. my data involves a three-level ordered outcome (see ...
101 views

### Using "moderately" correlated variables to select controls for a LASSO regression?

In medicine we often have a disease status as an outcome variable and a lot of independent variables in which we want to see if there is some connection. Traditionally, baseline characteristics such ...
168 views

### Potential bias when the training set is more general than the testing set

I am using Logistic Regression (LR) to obtain Coronary Artery Disease CAD probability equation. The data set has 16 candidate predictors, all continuous. There are two groups, CAD patient group (70 ...
959 views

### R: Quadratic Regression with interaction: when to center?

I have a statistical question. I have data from an experiment with two conditions (dichotomous IV: 'condition'). I also want to make use of another IV which is metric ('hh'). My DV is also metric ('...
446 views

### Is there any technique to explore the relevance of interaction terms to a regression before adding to the model?

As usually, I've got an independent ($y$) and many dependent ($x_{1}, ..., x_{k}$) variables. I'd like to add interaction terms to my linear regression, but the vast number of variables makes it ...
986 views

### Catagorical variables with very uneven distributions? Removal/modify/leave?

In my current dataset I have quite a few categorical variables. Most have decent distributions between the categories. 30:40:30 splits etc. where these are percentage of dataset members per category ...
575 views

### Permuting the formula argument to Hmisc:aregImpute

In Frank Harrell's RMS Short Course today, I became aware that multiple imputation with Hmisc:aregImpute is not invariant to the ordering of terms in its formula ...
94 views

### Logit Regression and F-test: Can I apply the f statistic when variables are non-normal and the output is binary?

I want to do a univariate analysis on a set of variables to see which predict a binary outcome. I want to discard some of them before performing logistic regression. I am trying to understand if I can ...
143 views

### Fitting model again after variable selection

This question has been asked quite a bit in other contexts (doing LASSO then OLS on selected variables for example), but I'm unsure about how to proceed for this case. Suppose I have a set of 50 ...
61 views

### What is the best way to choose interactions between continuous variables for Logistic Regression?

I have a logistic regression model that I am working on for a school project. I have about 55 predictors, all of which are continuous. I am relatively new to the idea of "interactions" between ...
1k views

### Confusing aspect of Harrell's bootstrap-based optimism-correction Internal Validation procedure

This bootstrap-based internal validation procedure is implemented in the validate function in Harrell's rms package. It allows ...
720 views

### Are variable selection strategies for regression useful?

I have read many posts (including Frank Harrell's book) about the consequences of using variable selection strategies. However, it seems that many of the published work in the medical field still ...
206 views

### Univariate and multivariate regression

I found a research article Nurses’ reports of staffing adequacy and surgical site infections: A cross-sectional multi-centre study and I want to know the reason why they used regression for their ...
358 views

### Do the problems of stepwise variable selection exist in FA, PCA, SEM?

Note: This is a revision of my original question. I have read the critique of stepwise variable selection and "all possible subsets regression" by Professor Frank Harrell here. Are factor analysis, ...
41 views

### Is having more features definitely equal to having a higher chance of overfitting?

I am doing a EEG data classification problem. Currently I am using the ANOVA test to help me select K best input features (with K a parameter to tune) and feeding the selected features into a logistic ...
80 views

### Violating Multinomical Logistic Regression Assumptions?

Dear Cross Validated Community, Our lab is trying to develop a classification-type model that categorizes chemicals into one of three groups using data from cell culture experiments. We have been ...
476 views

### Can I combine 10 variables into one variable before performing logistic regression on 18 total variables?

Univariate analysis of 18 variables possibly associated with spine infection--can all the historical variables be combined into one variable, then logistic regression be performed?
402 views

### Compare the results of two canonical correlation analyses (CCA)

I have four datasets: morphological measurements for a set of species (M1), ecological measurements for the same set of species (E1), morphological measurements for a second set of species (M2), and ...
263 views

### Ridge regression not appropriate for collinearity caused by mathematical constraints on the data

In this paper: Use of the Bootstrap and Cross-Validation in Ridge Regression Author(s): Nancy Jo Delaney and Sangit Chatterjee Source: Journal of Business & Economic Statistics, Vol. 4, No. 2 (...
289 views

### Correct order of performing imputation and variable selection

This is a general question about performing data analysis. I have a data set with ~1000 sample size and 200 features. Some of features have more than 50% missing or even higher. The missing pattern is ...
83 views

### Discovering transformations and interactions

I am teaching myself regression using Regression Modeling Strategies by Harell and the author goes at quite the length to showcase the importance of modeling interactions and transformations of the ...
32 views

We have developed a basic Regression framework where we try to build models for over 100 configs(stored in a file). To run : ...
33 views

### Combining mean differences in regressors and significant prediction and moderation in multiple regression

I am analyzing a survey about career choices with an eye toward demonstrating sex differences in: 1) the means for factors that might be related to career choice (e.g., differences by sex in ...
23 views

### I have a confusion between using 4 different general linear models and 1 singular ones. I have provided with the codes and outputs

I want to check the effect on mass of crickets, I have a fixed linear effect (AltitudeAge), fixed quadratic effect (AltitudeAge^2), random effects (Nymph IDs, population and the incubators they are ...
69 views

### Kaplan Meier Diagnostic Utility

I'm trying to understand a paper that claims to have identified a gene expression signature that can distinguish primary from metastatic tumors. The authors stratify their data into patients with and ...
46 views

### Method for testing interaction in regression analysis

I am running a linear model with 6 explanatory variables (5 in classes, 1 quantitative), and would like to test which interaction(s) are eventually significant. I think an ascendant stepwise method ...
666 views

### How to apply a model built using Multiple Imputation to predict on dataset with missing data?

I understand that Professor Harrell recommends using the target variable in Multiple Imputation. An example using aregImpute of the rms package is in his lecture notes: http://hbiostat.org/doc/rms....
57 views

### Including many interaction terms in a logistic regression

I have a logistic regression model that is currently of the form: Event ~ Vacc + Age I want to start including interaction terms for different types of vaccine. ...
50 views

### Interpretation of spline models: plot vs estimate

I have conducted regression analyses (cph - using rms package) to investigate associations between an exposure (air pollutant) ...
202 views

### Why is the penalty in the logistic regression likelihood ratio test different from the penalty I specified when fitting the model?

I'm fitting a penalized logistic regression model using the rms package in R. When I print the result, the penalty in the model likelihood ratio test is different from the penalty I used to fit the ...
724 views

### package 'rms' - singular information matrix encountered

I am trying to fit a binary logistic regression model using only one predictor. After consulting a loess plot I decided to use restricted cubic spline to fit the curve (with default 4 knots). Using '...
58 views

### Seeking regression modeling strategies for predicting prices based on categorical variables (one of which is ordered)

I have a question similar to this one, which never received an answer. Let's say I have widgets that have different quality ratings $q\in\{0,1,\dots,N_q\}$ and which are in different regions \$R\in\{...
73 views

### Can I treat ordinal values (with an underlying order) as continuous when extracting residuals and in exploratory factor analysis?

I am looking for clarification on whether it is acceptable to treat ordinal values with an underlying order as continuous when extracting residuals and in exploratory factor analysis (EFA). Does ...
122 views

### How to correct for selection bias caused by a prior version of a logistic GLM?

I've looked for information on this, but there are a lot of different angles to addressing selection bias I'm lost on how to proceed. Here is the basic scenario: We collect data on n customers. Of ...
81 views

### R or spss? For a conditional regression with 2 dependent variables?

Maybe you find my question a bit simple but I'm really confused as I'm not statistician. I have 2 SNPs (can be proposed 2 genes instead) that are related to a primary disease (like major depression), ...
92 views

### Dealing with "Don't know" and "missing" in the outcome variable

I want to use a generalized linear model for my analysis but the problem I am facing is that the outcome variable y which is categorical is not binomial since I have the following responses: Yes, No, ...
49 views

### Use R to perform a logistic regression and cross-validate in a small sample?

I have a small sample (n=69, 35 with diseases, 34 without disease). I have around 20 variables that came up as significant using indiscriminate univariate regression. Of these 20 variables, several ...
968 views

### Why does gvlma() give contradictory results for linear model assumptions?

I have fitted a linear model and I am checking the assumptions for which I get this diagnostic plot: From this diagnostic plot there seems to be an increasing variance in the residuals for increasing ...
1k views

### How to use aregImpute "group" argument?

Can someone provide an example of using the "group" argument with aregImpute()? I see that group=NULL is the default, but my data include a few factor variables with levels with <5 observations. My ...
61 views

### Assess a model building technique

I am confused about a certain model building technique that seems to exist, at least in practice (I am not sure whether it has its place in textbooks). Question 1: I wonder under what conditions or ...
960 views

### Estimation of theta for IHS (inverse hyperbolic sine) transformation

I am trying to use the IHS transformation to correct for heteroskedasticity in a Tobit model. The main references have been Pence (2006) and Burbidge et al. (1988). I have noticed that the convention ...
31 views

### 100mn rows of "events" with 30 or so attributes, want to understand what affects one particular attribute - how? which software?

I have about 50-100 million rows of data of interesting "events". Each of these rows has about 32 attributes. One of these attributes is how much money we made :-) What's the best way to make sense ...
15 views

### Repeated measures ordinal outcomes

I have an outcome that is measured at two time points, baseline and 1 year after. The outcome is on an ordinal scale: 3 = better, 2 = somewhat better, 1 = somewhat worse, and 0 = worse. I'm interested ...
8 views

### Converting a code for 5-fold cross validation to stratified 5-fold cross validation for continuous target variable

Do you know how I can convert my code so it can do stratified 5-fold cross validation on a continuous target? df['score'] or y is a continuous variable. ...