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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Fitting coxph survival model to replicates [migrated]

I am performing simulations fitting a coxph model to 1000 replicates. The code below uses a for loop to fit the data from one replicate to another. Is it possible to fit a coxph to all the 1000 ...
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Merging survival data with time varying covariates

In merging the data in R the censored observations are merged well but the observed subjects are not. For example, the second subject had an event at time 0.546. How can I merge the time varying ...
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84 views

Survival curve from time-dependent coefficients in the Cox model

I fitted a Cox Model that does not satisfy the proportional hazards assumption. Thus, I included time-dependent coefficients using the tt() function in the same way ...
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1answer
37 views

Can one compare Hazard Ratio and Average Hazard Ratio?

I would like to compare three predictors of survival by comparing three cox regression models. One model violates the PH assumption which brought me to weighted cox regression as implemented by ...
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deviance residual plot abnormal for cox proportional model

Hi, is the cox proportion hazard model violated? I'm not sure whether the problem is censored data or wrong prediction? But, there is only few significant variables can fit the hazard model adequately....
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35 views

Constructing hazard for x-year survival in cox models

If a person wants to assess the 1,5, or 10 year survival of a group of patients how should they consider right censoring for the patients? Between these 2 options what would be best for this 5 year ...
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53 views

Computing Chi-square values from Schoenfeld residuals

Based on page 164-165 of [Collett:Modelling Survival data in medical research (Third edition-2014)] the Schoenfeld for individual test and for global test can be obtained as follows[1]. However, ...
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92 views

How to calculate Schoenfeld Residuals in R

I am trying to manually calculate the schoenfeld residuals in Cox model. Please see the code below. Sresid gives the calculation in cox.zph function using schoenfeld residuals. Schoenfeld gives the ...
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91 views

Test for proportional hazards assumption in coxme model - Error and abortion of R session

I'm trying to do a survival analysis using a mixed-effects cox proportional hazards model in R with coxme. My data is - actually - fairly simple. I followed the survival of insect that were kept in ...
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66 views

How does time specific hazard ratios relate to time dependent incident dynamic ROC AUC?

I have a question related to time specific hazard and time dependent incident dynamic ROC analysis. I am currently working on some analysis where I evaluate a prognostic model (Cox model) on some ...
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70 views

Proportional Hazards Model and EM Algorithm

I am working with the standard proportional hazards model given by $\lambda(t|Z) = \lambda_0(t)e^{Z\beta}$ for a special type of data that requires an EM algorithm to estimate a discretized version of ...
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92 views

How to explain large hazard ratio confidence intervals?

I did a multivariable cox proportional hazards analysis including variables with univariable p<0.2 , and 3 variables gave statistical significance. Their HRs are around 5 to 8, which is pretty high,...
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105 views

Survival analysis: using time varying covariates for resolving violated PH

p1 is a factor p2 is a continuous variable Model m = Survival_function ~ p1 + p2 Both covariates - p1 and p2 - violate the proportional hazards assumption. I am ...
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25 views

Stratified KM curve plot for estimation of proportional hazards assumption violation

I am reading a paper that attempts to investigate time varying covariates in Cox proportional hazard model for breast cancer patients. I read that we can plot stratified KM curves for two groups of ...
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Likelihood term in Cox Proportional Hazards Model

I have just started learning on the Cox proportional hazards model. I understand that the hazard function is the multiplicative of the baseline hazard rate $h_0(t)$ and the hazard rates dependence on ...
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28 views

Cox regression - proportional hazards - time to event variable in database with one line per individual per year

I have a question regarding my Time to Event variable. Since I am working with time-varying variables (which can change every year), I use a data structure with one line per individual per year. ...
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What measure to use to compare stratified and non stratified Cox proportional hazards in R

I am doing past papers studying for an exam on medical statistics and am unsure about one of the questions. The question reads as follows: "Consider now a second model where we stratify by sex ...
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42 views

Closed form expression for survfit function used in R (Cox proportional hazard survival model)

I have a dataset of patient survival times that I am trying to predict based on n covariates X1...Xn (patient co-morbidities, other diagnoses, lab results) using a Cox proportional hazard model. I'm ...
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58 views

Efficient influence function in proportional hazards model

I was hoping someone could help me with this problem in the cox proportional hazards model. I am given the following setup. T is a non-negative random variable with continous distribution and hazard ...
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41 views

Cox PH non-proportionality: time-dependent variable?

I am performing Cox regression modelling, searching for predictors for various clinical outcomes. Now, based on Schoenfeld residuals test, some of my binary predictors have p-value <0.05 with ...
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34 views

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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91 views

Why do my survival curves generated by the Cox differ from Kaplan-Meier for the simplest model?

I was told, that the Cox with a single categorical covariate is equal to the Kaplan-Meier stratified by the levels of this covariate. But the two graphs below don't support it. I also use strata() in ...
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Is doing Kaplan-Meier for 2 curves equivalent to ajdusting for a covarite or stratyfing in Cox? I want the HR for my KM curves

Using the R terminology (but this is software independent statistical problem), is survfit(surv_object ~ rx, data = ovarian) returning 2 Kaplan-Meier curves the ...
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Survival Analysis - Hazard Ratios of One - Interpretation and Model Fit

I am using Cox Proportional Hazards for a set of data. I continue to find variables with hazard ratios equal to one. I understand that these variables are not hazardous/protective to the life of the ...
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Assessing proportional hazards assumption: p-value from coxzph() vs. visual inspection of plot of scaled Schoenfeld residuals with time

The coxzph() function in the R package Survival shows a significant p-value for violation of the proportional hazards assumption ...
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Can it be said, that in case of non-proportional hazards, Cox returns average hazard ratio over the entire period?

I have read two opposite statements about the hazard ratios obtained from the Cox procedure in presence of non-proportional hazards. One is that the HR for a certain covariate, that fails this ...
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Which method of handling non-proportional hazards (here: crossed KM curves in 2+ points) would you prefer?

I have an experiment, where I compare two groups over time in frames of the time to event analysis. The Kaplan-Meier curves cross 3 times. It means, that the hazards ratios switch to the opposite side ...
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Why is there a linear and non-linear component of a pspline?

I am trying to fit a cox proportional hazards model with several categorical and one continuous covariate. The plot of martingale's residuals from the null model against the continuous term suggests ...
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Sampling data from a Cox proportional hazard model [duplicate]

Is it possible to simulate event time T from a distribution that depends on two variables A and Z but the hazard function conditioning on A only follows a proportional hazards model?
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31 views

All p-values rendered non-significant in Cox model after initializing coefficients from glmnet

I have a set of 200 genes that are split into numerical high and low, encoded as (1/2). I have set this variable this way for linearity of the model. Also, stratified by cancer and normal cases. I ...
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65 views

How to model competing risks with frailties in R

I am trying to figure out if (a) a competing risks model with frailty-terms is the right method for my data and (b) how to estimate such models in R. My data consists of N ~ 150 individuals with a ...
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119 views

flexsurvreg - shape and scale proportional hazard model

Please see below codes and plot for fitted curves to Kaplan-Meier data (weibull in this example) using the ovarian data. Based on the estimates, the shape and scale of the fitted Weibull distribution ...
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253 views

hazard ratio: are they normally distributed?

I am looking at forest plots (in the context of meta-analyses of clinical trials). I see values for hazard ratios, together with 95% confidence interval. My question: to compute this confidence ...
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56 views

Cox PH hypothesis and time-dependent covariates

The dataset I am working with is of this form: ...
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250 views

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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Point estimate for exponential of two variables

a proportional hazard model has two binary covariates. X1 for treatment (placebo and active drug) and X2 for gender. X1=1 for active drug and X2=1 for male. The estimated parameters are β1=0.4 and β2=-...
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673 views

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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64 views

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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1answer
187 views

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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47 views

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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1answer
144 views

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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1answer
83 views

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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1answer
40 views

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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84 views

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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1answer
221 views

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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294 views

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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1answer
47 views

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 ...