Questions tagged [cox-model]
Cox proportional hazards regression is a semi-parametric method for survival analysis. No distributional form needs to be assumed, only that the effect of one-unit increase in a covariate is a constant multiple.
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AIC of a weighted cox regression model (coxphw)
I have to compare three cox-regression models.
However, one of these violates the PH assumption. Stratfying the variable did not work because it is already categorical. Thus, weighted cox regression ...
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Multivariable Cox Regression Analysis
I would like to know if in multivariable Cox regression analysis there is a way to yield only models that include a variable of interest (and if no model is statistically significant to just answer ...
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Generating censoring times for the cox proportional hazards model
I am trying to understand the different ways of simulating survival times in a cox proportional hazards model. A simple example consists in simulating the event times following a Weibull distribution. ...
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Feature selection for Cox Model with low event number
I am interested in wether a set of 30 variables can predict OS in cancer. I have reduced my features to 15 after checking for multicollinearity. The problem is, I only have around 70 events in my data ...
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What are criteria to select the variables to include in a multiple Cox regression model
I have a group over about 500 subjects and want to perform a cox-regression to find predictors of an event taking into account the time to event. I have 12 potential predicting variables that I want ...
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Is it possible to calculate conditional PD / unconditional PD from Hazard Rate?
I'm just wondering that can I convert hazard rate to probability of default? Suppose I have the lifetime table data as per below:
Time
Total
Default
Non-Default
At Risk
0
-
-
-
356,335
1
5,587
1,...
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How best to analyze length of stay data in a hospital-based RCT?
I am interested in knowing whether or not there is a consensus about the optimal way to analyze hospital length of stay (LOS) data from a RCT. This is typically a very right-skewed distribution, ...
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How to Model Installment Payments with Different Durations Using Survival Analysis?
I'm working on a problem where I need to model the likelihood of future payments for various installment plans using survival analysis. The data I have consists of installment payment plans (or ...
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Cox PH controlling for multiple events
I'm working on a cox proportional hazard analysis in R using the survival package.
I´m analysing covariate effects on fish movement within a study area. The study area is divided into two zones ("...
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Cox proportional hazards model and dummy variables
I have some doubts while doing this question.
I tried out parts (a) - (c) and am quite confused by (d).
Would appreciate if someone can help to check my work to see if I have done it correctly, ...
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How to create a Cox proportional-hazards model with count data and proportions?
Suppose I have data with the following format:
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difference between a cox regression with a time varying covariate and discrete time cox model
I am curious about the difference between a discrete-time Cox model and Cox regression with a time-dependent covariate. My dataset includes a single event variable and a binary covariate, as shown ...
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Weighted Cox regression: test for goodness of fit?
I want to do a weighted Cox regression analysis (coxphw command in R) since there is violation of proportional hazards assumption in standard Cox model shown by Schoenfeld residuals. What would be the ...
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An error in formula proposed by Riley et al to calculate the sample size
I used the following function to find the minimum sample size for a cox proportional hazard ratio (proposed by Riley et al). Surprisingly, the estimated number of events is more than the expected ...
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Interpretation of coxPH model with and without splines for non-linearity
I am fitting Cox Proportional Hazard Models to investigate the impact of external, military support (my covariate) on the "risk" of a peace agreement (my event of interest) after civil war.
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Interpretation of Cox Hazard Model with quadratic term
I am having trouble finding information on how to interpret coxph model hazard ratios with a quadratic term. Some of my variables are continuous count data, whereas others are continuous percentages.
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Simulate a survival dataset with specific events and HR for multiple variables
In my teaching class, students need to read and comment on a scientific article.
The next lesson is a coding lesson, and I would like them to recreate a plot from this article, so that they understand ...
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Cox Regression model with time-dependent covariates - violated assumption of proportional hazards (PH)
I am currently performing some Cox regression models. The image attached shows a Schönfeld residual based on one of the cox models with a significant p-value which means that the proportional hazards ...
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Cox Proportional Hazards with multiple failures
I have a dataset of subjects that can fail, recover from it, and fail again. How should I put this into a CoxPHFitter and ...
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Understanding survival curves with time-dependent covariates
In an observational cohort study, I want to assess the impact of exposure to a given prescription drug on mortality. Out of 841,161 patients, 150,279 (17.9%) died during follow-up. Exposure is a time-...
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If I want to adjust survival analysis for a covariate, like age, should I add it "smth+age" or add an interaction with it "smth*age"?
I have a survival analysis with a categorical predictor called "smth". I want to adjust it for age. I don't have any idea if they can interact or not but I guess they can. Now, about the the ...
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Time dependent covariates in Cox model
I am studying how to handle survival data when the follow-up is long. When I have a long follow-up, the assumption of proportionality of HR in the Cox model tends to fail, because the covariates ...
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Survival Analysis to Forecast Attrition
I have 5 years of historical data. I need to build an model forecasting attrition for the next 3-5 years. I want to build a survival analysis model, but need to know if I can estimate the attrition (...
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Counting process approach in survival analysis with non-contiguous intervals?
I am setting up a Cox Proportional Hazards model in R to analyze survival time until a recurrence event occurs. Each case can experience multiple recurrence events, therefore I decided to emply the ...
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Missing Data on Survival Analysis
I want to run a survival analysis (say, Cox model) with time of origin at birth and a disease (say, cancer) as the event,. Covariates are around 5 demographic variables (age, sex, etc.).
The problem ...
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Does it make sense to convert the Y-axis by exp() on the smooth scaled schoenfeld residual plot?
I posted a question on Stack Overflow. But the question got closed as the person who closed it wrote that it should belong here in Stack Exchange. I'm not sure why but here is the link for the post. I'...
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Cox Model - How to overcome small risk set after some time?
I am currently designing an Anderson-Gill model. After plotting the mean cumulative function (see below), I noticed that the confidence intervals become very large later, indeed too large for my ...
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Cox proportional hazards follow-up length
This is probably a basic question, but here goes:
I have a data set with a group of at-risk patients (for illustrative purposes lets say for heart disease) who were enrolled in a databases, some were ...
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Survival analysis for survey (case-control?) data
I have a dataset comprising approximately 500 patients with about 10 different diseases, potentially with correlated outcomes, and 200 healthy controls. Patient data is sourced from the hospital, ...
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rms::val.surv function estimated the same survival probability for all cases
I have fit a cox regression model, and used val.surv function to plot calibration plot to compare observed survival probability with predicted survival probability.
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Cox Regression - Output at Individual (observation) Level
I am building an attrition model. I was able to run the following cox regression. The rate of attrition looks very low, but I am only basing that on the plot I ran below. I would like to get a ...
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How to deal with left truncation in cox model in R
I have a longitudinal data with 8 follow-ups. My aim is to see the effect of a disease on ability decline at old age. In my study, I have sibling pairs, one with disease (1) and one without disease (0)...
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Newton-Raphson on Cox PH
I am currently working on my research, namely comparing the conventional optimization method, namely Newton-Raphson, in estimating Coxph parameters with the SGD optimization method. What if I want to ...
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Hazard Ratio from two cox models
I am working on a dataset from a clinical trial where patients received either treatment $A$ or treatment $B$. My goal is to develop two separate Cox proportional hazards (PH) models: one for patients ...
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Cox regression baseline risk and interpretation of coefficients
I recently encountered a problem with Cox regression that I couldn't find an answer to (please direct me to the appropriate resources if you know of any). So the problem goes as follows:
I have a ...
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How to understand the plotting of the cox.zph function in R?
I use a Cox proportional hazard model (coxph()) which gives me HR of about 2.9 for presence of factor B (factors can be A, B, C, A as baseline in the model), with ...
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Time related categorical variable for cox regression
I am trying to fit a Cox regression model to my time-to event data and besides other subject specific variables, I have two specific calendar dates that I want to analyze the effect of. For these two ...
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Dropping a level of a categorical variable with small number of subjects on cox regression
I am trying to fit a Cox regression model to my time-to event data and have a categorical variable with 5 different levels. I leave one level out as the 'reference'. I also have 2 levels with small ...
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Dealing with categorical variables on cox regression
I am trying to fit a Cox regression model to my time-to event data and have a categorical variable with 5 different levels. If I don't leave one of the levels out, then I will have multicollinearity, ...
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How to explain Hazard Ratio in layperson's terms
In the context of a Cox regression, I recently heard someone say that "the hazard ratio of 0.70 between the two treatment groups indicates that, during the whole followup time, of 100 persons in ...
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Risk score calculation from coxph regression with multiple imputation dataset
I am conducting survival analysis on a dataset with less than 5% MCAR data. I have performed multiple imputation on this dataset and now I want to run the Cox proportional hazards model (coxph) in R. ...
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Multi State Survival Analysis Transition Between States Triggered By different events
I have a state diagram for multistate survival analysis, and between 2 specific states, I have 2 types of transitions triggered by different types of events, i.e, from state 1 to state 2, the ...
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How to Replicate Survival Analysis Conducted in Stata to R
I am curious on how to replicate the results of a Cox model estimated in Stata in R. I get completely different results, and I think I understand why (but I am unsure of how to fix it), but before I ...
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Baseline covariates with age as time scale in survival analysis
I’m looking for the correct way to incorporate baseline information in a survival analysis when using age as the time scale (or confirmation that what I'm saying in the following is correct).
Clearly, ...
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Surival Prediction - Train/Test data vs Production data
I have a need to create a churn prediction model and it seems like a survival model fits the bill since my data is right-censored (there are many customers who have yet to churn, or in other words, ...
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Dealing with Low variance categorical variables on cox regression
I am fitting a time varying cox model to my survival data, and I remove one arbitrary level from each categories, to create the baseline hazard. I have some low variance categorical variables. If I ...
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Discrepancy between ggsurvplot predicted survival curves and raw data
I'm using a Cox proportional hazards model to look at the relationship between coyote survival and various environmental factors.
The model summary indicates that the proportion of natural habitat has ...
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Merging Different Groups for Cox Regression
I have time to event data for subjects from different groups, and I use group features as covariates for cox regression. For example, I have 100 subjects from group A, and 200 subjects from group B, ...
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Would you used prediction from Cox or stratified KM for drawing survival curves and testing them?
Let's assume I have an experiment, where I track some event. I want to analyse the time to this event between two levels of a group G: g1 and g2
I want to do the comparative analysis in sub groups, ...
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Interpretation of hazard ratios - impact on time to event?
say I use Cox proportional hazards model where I explain time to some event with a number covariates. In the result, for each covariate I get the proportional hazard ratios (HR). A HR lower than 1 ...
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