All Questions
Tagged with cox-model proportional-hazards
52 questions with no upvoted or accepted answers
3
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Proportional hazards assumption for cox regression - global test or graphical assessment
I have run a cox regression with only a treatment in mind so far and have then tested the proportional hazards assumption along with a graphical assessment using the log-log survival plot. My global ...
- 126
3
votes
0
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135
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interpretation of cox HR under non-proportional hazard
When the true hazard ratio $\lambda(t)$ is time varying as shown below, I used a standard cox regression to get a hazard ratio. If the hazard ratio of $\lambda=0.78$, how can this value be interpreted?...
- 31
3
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0
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347
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How to manually calculate concordance for a coxPH model
I am struggling to work out how the concordance statistic of a coxPH model is derived.
I have built a coxPH model on a small dataset (4 observations). The resultant model is given below:
...
- 61
2
votes
0
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93
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Proportional hazard assumption: graphical approach vs subsampling
Hopefully someone can guide me on the following.
I have a large dataset (> 151k firms with multiple observations per firm).
My dataset looks at firm failure using counting process style and my ...
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2
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0
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74
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How do I complete a sensitivity analysis to simulate censored data?
I am currently trying to analyze the duration of the egg stage of two species of insect (factor 1; 2 levels - HA and AP) at several different temperatures (factor 2: 5 levels - 20, 23, 26, 29, 32) ...
- 461
2
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0
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164
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Step functions for non-proportional hazards
I have a stratified Cox model with covariates ("big") which violate proportional hazard assumptions:
...
- 31
2
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0
answers
299
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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 ...
2
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0
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110
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Check if PH or AFT model should be fit
It is unclear to me when it is appropriate to fit an accelerated failure time (AFT) model rather than a proportional hazard (PH) model.
I've tried googling and it appears as though PH models are ...
- 635
2
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1
answer
2k
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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.
...
- 31
2
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0
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521
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Cox Regression in Propensity Score Matched cohort after multiple imputation
I have a follow-up question on the question of this thread:
Manipulating data for propensity score matching following multiple imputation with mice package
In aforementioned topic we can see the ...
- 91
2
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0
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216
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What variant of interaction when the PH assumption is violated in a CoxPH Model?
When the assumption of proportional hazards is violated, the suggestion is to interact offending covariates with time (or a function of time). In this blog post, the author suggests to include only ...
- 53
2
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40
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Cox-Hazard Ratio differences in Software suits; Manual calculation
Working in clinical research my task is to calculate the Hazard ratio, better to check the calculations of someone else. This first calculation was based on ARM=(3 different treatments) with only t=(...
- 117
2
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0
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1k
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Predicting Lifetimes using CoxPH
I have a dataset of about 9k rows and 60 features (columns). I have a binary status column (1 - dead, 0 - alive) and a lifetime column in days which is right censored. I am currently using the cox-PH ...
- 121
2
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0
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214
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How to interpret insignificance of time-varying coefficient and main effect
I have a survival-time dataset where entities (countries) are measured at discrete intervals (years). I'm interested in examining the effect of some fixed treatments (i.e. ones that occur at the ...
- 143
1
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0
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59
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Testing Proportional Hazards Assumption in Cure model
I am currently working on estimating a cure survival model where I want to incorporate a Cox proportional hazards (PH) model for the latency part of the model (i.e. the part for the observations that ...
- 363
1
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0
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14
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Difference ACD and Survival Analysis models
Autoregressive conditional duration (ACD) models are typically used in econometrics for dealing with trade duration (TD) data and it is used to capture the clustering structure.
In other areas of ...
- 363
1
vote
1
answer
794
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Compare two hazard ratios from two subgroups?
For example, for the smoker group, a cox regression shows that the hazard rate of alcohol use on survival is 1.41. In the non-smoker group, another cox regression shows that the hazard ratio of ...
- 41
1
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0
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84
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Help interpreting Bivariate Cox Proportional Hazard Model results
I have done an analysis using Bivariate Cox Proportional Hazards Model Regression, to estimate the rate of exits from unemployment for people with mental illness relative to people without mental ...
- 11
1
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0
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379
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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:
...
- 101
1
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0
answers
241
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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 ...
- 11
1
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0
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39
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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:
...
- 11
1
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0
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19
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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?
...
1
vote
1
answer
141
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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 + \...
- 479
1
vote
0
answers
575
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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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1
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0
answers
118
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Hazard ratio endpoint vs Odds ratio
This study (https://academic.oup.com/cid/article/65/1/100/3097834) seems to conduct a cox proportional hazard regression on survival data, but reports hazard ratios for 30- and 90-day mortality:
...
1
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0
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134
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Test assumption of common baseline - Adersen-Gill Cox regression?
I'm running a Andersen-Gill recurrent (multiple events) cox model and I want to test the assumption of common baseline across events. Is this as simple as entering 'event' into the model and checking ...
- 113
1
vote
0
answers
87
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Frailty or median values in my cox proportional hazards model?
I am analysing data of woodpecker-made holes and I am interested in seeing what covariates and to what degree affect the survival of these holes (otherwise known as cavities). However, I encounter the ...
1
vote
0
answers
1k
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How to calculate the cumulative baseline hazard function for a CoxPH model
I have read that the following formula is used to estimate the cumulative baseline hazard function:
I also know that the basehaz command in R will also calculate an estimate for the cumulative ...
- 61
1
vote
0
answers
126
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I multiplied a predictor variable by 10. Why does my univariate cox regression HR and p-value change entirely?
I calculated the waist-to-hip ratio from, well, waist and hip measurements in cm. The ratio's values would come out in the range of 0.8-1.1, for my population.
When I performed a univariate cox ...
- 33
1
vote
0
answers
410
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Time scale in survival analysis
I am doing a churn analysis of some bank customers with survival analysis.
Right now I am using the customers' years in the bank [0;17] as time scale, and then use the customers' entry age as a ...
- 31
1
vote
0
answers
95
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Cox proportional hazard - can hazard be treated as instantaneous probability?
I'm doing a question on cox proportional hazard models that at the very last step leaps from hazards to probabilities, and I'm not sure how it does this. I've paraphrased it below to keep it simple, ...
- 2,589
1
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0
answers
562
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Cox regression slope - understanding the sign of the slope
I am using the coxme package in R to perform mixed effect cox regression analysis, and would greatly appreciate some advice on how to interpret the regression ...
- 892
0
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0
answers
16
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Cox-like model: weighted sum of proportional hazards
We are trying to do inference on vaccine effectiveness (VE) during an epidemic in a risk-stratified population.
Models:
Consider the Cox model:
$$ \lambda_{ik}(t) = \lambda_0(t) \exp [\beta X_{ik}] $$
...
- 217
0
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0
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34
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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 ...
- 57
0
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0
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15
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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, ...
- 57
0
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1
answer
29
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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 ...
- 57
0
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1
answer
209
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Lifelines-CoxTimeVaryingFitter for Multistate Survival Analysis
I am new to survival analysis and cox regression, and have limited statistical background. I have time-to event data for a multistate survival model and I want to fit a cox model for each transition ...
- 57
0
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0
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72
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Interpreting hazard ratio in table
This poster has been making headlines lately due to its subject and conclusions. Specifically, I'm interested in understanding how the hazard ratios are being calculated in this table:
For example, ...
- 649
0
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0
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14
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Disaster exposure as treatment in survival analysis - multiple "treatments" / pre-"treatment" trends (in R)
I am looking at using a cox proportional hazards model to look at migration after disasters. I have two disasters at T1 and T2 (which are two years apart). I created two models looking at the risk of ...
- 399
0
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0
answers
23
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Why such a large difference between Odds Ratios and Hazard Ratios?
I am studying the risk of dementia secondary to hearing loss. I have fashioned a Cox time-dependent model with multiple covariates, all with factor levels, but have also done a logistic model for ...
- 1
0
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1
answer
317
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Cox survival PH violated variable is part of an interaction
One of my main predictors violates the PH assumption. I've been reading different ways to deal with this for a while and have decided on an interaction with time after making a person-period file (...
- 11
0
votes
1
answer
98
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Use an arbitrary number of features to predict an individuals life expectancy
Objective
I want to predict someone's life expectancy (age they will die) based on their lifestyle, current conditions, medications, biomarkers etc.
Limitations of supervised learning
There are no ...
- 139
0
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0
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147
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Violation of PH assumption Cox model
So, i have seen similar questions to mine here but still can´t quite understand why this is happening.
I´ve ajusted a cox model and now i´m testing the PH assumption. This are my results:
It is ...
0
votes
1
answer
108
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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 ...
- 103
0
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0
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253
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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 ...
- 33
0
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1
answer
251
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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 ...
0
votes
0
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102
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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 ...
- 131
0
votes
1
answer
741
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Checking PH assumption for a time dependent (T_COV) variable in a Cox PH-regression: with or without the original covariate in the regression?
I am performing a cox proportional hazard regression on survival, in a sample in which almost everyone dies in the follow up period. I have little knowledge on statistics in general but i am reading ...
0
votes
1
answer
37
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Competing Risks Likelihood in each State
I have a competing risks model where every observation starts in state 0 and ends up in either state 1 or state 2.
I have the following cumulative hazard functions for each transition to state 1 and ...
- 133
0
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0
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131
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Cox hazard Model: HR of 1 variable greater than 1 in simple regression becomes smaller than 1 in a multiple regression
I'm performing a simple and multiple Cox regression. I have 1 dependent variable
$y$ and 10 independent variables:
$$X = x_1, x_2, x_3, x_4, x_5, x_6, x_7, x_8, x_9, x_{10}$$
A particularity of the ...
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