Questions tagged [proportional-hazards]

Proportional hazards is an assumption of the Cox proportional hazards model of survival analysis and some other models as well. The assumption is that a linear increase in the predictor will have a uniform multiplicative relationship with the hazard.

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Is the proportional hazards assumption violated (interpreting Schoenfeld residuals)? What is my best option if so?

I am using an extension of the Cox model in the counting process format (Andersen-Gill model), with time-dependent covariates. The analysis is investigating the effect of an intervention on hospital ...
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How to model survival analysis when proportional hazards assumption is not met and stratification and time-varying are not possible?

I am modelling a survival analysis over a rather long follow-up period (10 years). My exposure is time-invariant and clearly violates the proportional hazards assumptions so Cox Proportional Hazards ...
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Is it possible and how to predict individual survival curve after Cox regression?

Taking the veteran dataset of a two-treatment, randomized trial for lung cancer in the R package survival as an example, where <...
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Simulating Proportional Hazards Weibull model with 2 binary variables, incorrect estimation?

I am simulating survival times from a Weibull(5,3), and I also simulate 2 spurious binary covariates. When I fit a proportional hazards model with Weibull baseline, ...
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Which function of time to use in a Cox Regression for time-varying coefficients?

I have a Cox regression model where the outcome is a non-recurring event. Within the model, two categorical variables violate proportional hazards, and I have currently extended it to account for time-...
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Doing Cox univariate analyses followed by multivariable analysis on significant variables?

I have collected a dataset on a group of patients with a rare disease where not much is known. These patients can have an outcome, X, which has been seen in 50 of the 300 patients. I want to find out ...
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Baseline hazard and survival curves in Cox regression [duplicate]

The idea behind Cox regression in survival analysis is that it does not require knowing the baseline hazard rate, $\lambda_0(t)$. Yet, one often needs this rate, and many software packages do estimate ...
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Relation between hazard and survival functions

I have recently began using pysurvival package, for standard Cox regression. Their CoxPHModel predicts both the survival and the hazard functions, which I would ...
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Cox proportional hazard (non-inferiority hypothesis testing) in R

I have researched this question for hours. Any help is appreciated. I am using the "survival package" in R with coxph function. I will illustrate with this example ...
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Understanding Cox regression

I have to work with Cox regression but I'm not getting fully how it works. So I created a very basic fake data sample, and tried to fit a Python Lifelines ...
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Unbiased coefficients in Cox Model if proportionality violated?

If a Cox PH Model is specified we should always check the Proportionality assumption. It's obvious that, if it is violated the coefficient for the covariate this is the case for is not the efficient ...
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Test linear trend for hazard ratio

I used Cox proportional hazard models in R to calculate the hazard ratio (HR) of smoking for cardiovascular disease (CVD) in a population. Then I made subgroup analysis by age (20-30,30-40,40-50,50-60,...
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Is the interpretation of hazard ratio on continuous scale (without information on each increment increase) same with each increment increase?

fellow statisticians. I know that my question seems so general, and may be similar to previous questions. However, I did not find any previous questions explicitly asking/answering my question. I am ...
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Cox proportional hazards with multiclass dependent variable

Is it possible to perform a multiclass Cox proportional hazards model? I'm interested in finding the probability of self cure on consumer loans, or just study how self-curing clients behave so as to ...
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Obtain period-specific hazard ratios in a (piecewise) Cox regression

I am a performing Cox regression. The output of such regression is a hazard ratio. In my case, the HR changes over time, so I want period-specific HRs in specific time intervals. I am unsure how to ...
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What does the output of flexsurvreg, for a Gompertz proportional hazards model, mean?

I am estimating a Gompertz proportional hazards model in R using the package "flexsurvreg", but I'm having a hard time understanding the output of this function. My dataset is collected from ...
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Modelling likelihood of failure

My goal is to assign vehicles a “risk” score (perhaps on a scale of 1 to 5) based on their history. I have data on the vehicle’s age, model, mileage, and dates it was repaired. This risk score would ...
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how to prepare time to event value in case of longitudinal data for Survival Analysis

I have longitudinal transaction data of a retail store where each row is a transaction done by an individual. I would like to perform a survival analysis to analyse how long a customer will transact ...
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Cox regression for non-repeated events with panel data

I have a question with regard to the research design for a research paper I´m writing on. The data comes in the following form: ...
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Cox regression assessing joint relationship between baseline groups? JAMA example

I'm a new R user trying to better understand the analytical framework behind an important JAMA paper (doi:10.1001/jama.291.2.210) and how it can be coded in R. It's objective was to evaluate if, in ...
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170 views

Cox regression. Find 95% confidence interval for comparison of two groups

I am working with pbc dataset in R and would like to build 95% confidence interval for the comparison of two groups: 60-year-old males on DPCA with bilirubin = 1 mg/dL 40-year-old females on placebo ...
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Calculate effects on survival time from Cox proportional hazard model?

Novice stats question here: When I run a cox model over daily survival data as a function of 3 covariates, the results: ...
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What could explain radically different HRs and ORs with similar absolute probabilities

This is a weird question that may not have a good answer, but I thought I'd take a shot. In this clinical trial (hereafter, the ACTT-I Trial: https://www.nejm.org/doi/full/10.1056/NEJMoa2007764), it ...
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assumptions of the mixed-effects Cox regression model

In typical Cox proportional hazards models the assumption of proportionality can be tested using the function cox.zph() in R, but I am doing a mixed effect cox model with the coxme function in R. Is ...
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Cox proportional hazards model with inverse probability treatment weights: testing the Cox proportional hazards assumption

I have survival data of persons who participated/didn't participate in a health promotion program. To estimate the effect of the health promotion program on the hazard of mortality, I plan to use a ...
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Generating quantile-type predictions from Cox Proportional Hazards model

I am trying to generate quantile-type survival time predictions from a Cox proportional hazards model, similar to those generated from: ...
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Limit on number of features in Cox Proportional Hazards model with penalized spline

I am trying to fit a Cox proportional hazards model with penalized splines using the survival R package with the following, but it seems like I am hitting a limit ...
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How to interpret HR under non-ph

How do I interpret a HR under non-proportional hazards? Sounds silly, but I couldn't find a clear answer. Allison 2014 calls it a rough average. How is this average rough, and not a real average of ...
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Why is cox.zph splitting terms?

I'm using survminer to try to create a survival formula for a phenotype data set. ...
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Proportional hazards model with lognormal baseline hazard in R?

I would like to fit a proportional hazards model with log normal baseline hazard in R. I have found several options for the semiparametric Cox proportional hazards, but I have not found a package to ...
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How to go about interpreting time-varying co-variates in survival analyses?

I'm pretty new to stats.. been working with cox models and getting a little confused. 1) Why do they occur? 2) How might one interpret/clinically translate a time-varying co-variate for cox models? ...
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Cox proportional hazards. What does constant over time mean?

I am studying the Cox PH model. But there is one thing I cannot seem to wrap my head around. In the Cox PH model, we want the hazard ratio to be constant over time. But what is time in this case? ...
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Choosing a distribution for parametric hazard modeling

I have a question concerning determination of the baseline hazard function in a parametric survival regression such as Exponential, Weibull, e.g. Is there a way to determine which one is best? I have ...
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Error “system is computationally singular” when running cox.zph for a Cox Model

I have built an extended Cox Model in R, with time-dependent covariates, as described in this R vignette. I have built the model by running the following: ...
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How to prove that the likelihood of a proportional hazards with lognormal baseline model is log concave?

I want to fit a survival model using a proportional hazards assumption $$h(t) = h_0(t)\exp(x^T\beta),$$ where $$h_0(t) = \dfrac{\frac{1}{\sigma t} \phi \left(\frac{\log(t) - \mu}{\sigma}\right)}{\...
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Is this approach the right one in Cox with time-dependent covariates in R?

first of all I would like to thank you for reading my post. Then let me describe my situation: I'm trying to develop a Cox model with time-dependent covariates. I have a dataset of patients with ...
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Estimating age group specific hazard ratios from cohort data with left and right censoring

Background on the data: I have a dataset from a cohort of hundreds of thousands of individuals. Variables of interest included are: age at start of follow-up, disease endpoints, age at endpoint or ...
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How to interpret left and right censoring

I am fully aware that question regrading left and right censoring has been asked before. I will however post my own question, as I believe that its focus differs significantly. Here goes: I have a ...
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Violation of Proportional Hazards Assumption by a Continuous Variable

I'm constructing a multivariable Cox model and I am trying to assess whether the assumption of proportional hazards is valid using scaled Schoenfeld residuals (using ...
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Scaled Shoenfeld Residuals

When constructing a multi-variable Cox model, is it necessary to check the proportional hazard assumption for each covariate individually by first fitting a univariable model and checking the ...
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Is Cox Proportional-Hazards model appropriate for discrete time points

I'm dealing with medical data and I'd like to determine the dropout rates at about 10 different time points. Further I'd like to see the effect of various covariates on the dropout rates. Would a Cox ...
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Kalbfleisch Prentice survival calculation for Cox PH model

A method to estimate survival probabilities for a Cox PH model comes from Kalbfleisch and Prentice. It is explained in their 2002 book on page 114. They present a formula for the likelihood in terms ...
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How robust is coxph when the proportional hazards assumption is violated?

How robust is the coxph when I don’t have proportional hazards? How common is non prop hazards and how do I fix it? Does transforming variables help? Does non parametric survival analysis handle non ...
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Is the Breslow estimator over-adjusted?

In a proportional hazard model with a Breslow estimator, I wondered why do we adjust on covariates in the cumulative hazard and in the model. On these few lines from Xia et al.[2], we can see that ...
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Cox PH - R 'rms' package - Concordance (Train, CV & Test)

Please could someone verify if my methodology for calculating these three versions of concordance are correct when using the rms package? I have really struggled to ...
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354 views

Checking PH assumption using scaled Schoenfeld residual tests

My cox model violates the PH assumption (according to cox.zph test), and I'm trying to interpret the scaled Schoenfeld residual plot, but I've never seen a plot with points lying in such a flat manner....
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Cox Proportional Hazards - Survival Function Estimation (on new data)?

I understand that the relationship between the hazard function, the baseline hazard function and the covariates is the following: $$ ln(\frac{h(T)}{h_0(T)}) = \beta_1 x_1 + \beta_2 x_2 + \dots + \...
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222 views

Case-Cohort analysis in R

I am attempting to conduct a Case-Cohort analysis with Cox's Proportional Hazards Model. The data set looks similar to the one below: ...
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Why is the exponential function used in Cox regression?

I am trying to get my head around Cox regression. I found quite a good paper on the subject by R. Tibshirani: A plain man's guide to the proportional hazards model. On page 66 he states: For ...
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Continuous Variable No Longer Follows PH Assumption When Categorized

I am creating a cox regression model with multiple covariates. I have two models: model A contains my variable of interest in its original continuous form, and model B contains my variable of ...