[Cox proportional hazards regression][1] is a very popular, semi-parametric method for survival analysis.

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What is the right way of computing baseline hazard rate

What is the right way of computing baseline hazard rate? To my understanding hazard rate at time t is simply #events / #AtRisk ...
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19 views

AIC values “Without Covariates” in R [on hold]

I've been using SAS but I'm now transitioning to R. When doing cox-regression in SAS (proc phreg) the output included AIC values "Without Covariates" and "With Covariates": The difference between ...
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Check hazard proportional assuption in a large coxph

I would like to check hazard proportional assuption in a large coxph. Usually I check it with cox.zph but with large coxph my p-value are very small whereas the log(-log(S(t)) curves are almost ...
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11 views

Interpretation of non-significant parameters in significant Cox-model as prognostic factors

I want to analyze predictive factors for patient survival after surgery. I have variables that are based on investigations at the time of the surgery, known predictive factors (age, KPS) and data on ...
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19 views

P-value from proportional hazards regression object [closed]

I'm running some proportional hazards regression models using the survival package in r and would like to know how I can access ...
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12 views

Dummy variables and intercept in Cox regression

I am working with the Cox Proportional Hazards model. Where the covariates include 2 categorical variables. Assume each category has 3 levels, so I model these in terms of dummy variables. Category ...
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15 views

Comparing survival times in small samples for two groups

I am working on a dataset of big cats. 18 cats have a particular antigen and the rest (58) do not. We have contact times for when blood samples were taken - so when the cats were identified as having ...
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61 views

Interpretation of the hazard ratio in a spline model on continuous exposures

I am having trouble interpreting the output from a Cox proportion hazard model with a spline term on a continuous exposure. In the below example (pseudo-code from ...
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40 views

how to interpret log transformed variables in survival analysis?

Suppose I have the following models: fit1 <- coxph(Surv(y,cov)~x,data=records) and ...
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Survival analysis coxph using ridge regression with 2000 variables => “Penalty terms cannot be in an interaction”

I'm doing a survival analysis using coxph function (package survival). I'm using a ridge regression model included 2000 variables but I have a type of error message "...
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51 views

Different “end of study” times for different cohorts - Cox PH model in survival analysis

I have a dataset with 4 cohorts of about the same size (~700 people each). I'm trying to apply a Cox PH model using the time needed to pass a very difficult exam as my "time" variable. The cohorts ...
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25 views

Proportionality assumption test (SAS) for categorical predictors

For Cox regression with all categorical predictors, I want to model time-dependent covariates (time*cov in Proc PHREG) to ...
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1answer
20 views

Can you use event history analysis if your sample was selected on the dependent variable?

I have a dataset that includes a random sample of individuals who are currently in a relationship in the United States. I also have data on the date that they met their partner and the date that they ...
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10 views

ROC and post estimation COX Harrell's C using your dataset

I have built a predictive model using a combination of logistic and cox regression models. I did it using a dataset of about 5000 records. I would like to calculate the AUC and the Harrell's post ...
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12 views

What are valid ways of analysing predictors for a response variable that changes with time?

I have a cohort of similar patients who are likely to get a certain disease over time. I am trying to find out how some continuous health markers (e.g. weight) at time 0 are related to their disease ...
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55 views

How does left truncation affect the calculation of the logrank statistic for comparing two survival curves?

I'm currently doing survival analysis in R with left truncated data and am having trouble understanding how truncation affects the shape of a survival curve, and the results of a logrank test which ...
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19 views

Cox PH Modelling: How important are ties to the end result?

I am working on create a survival model using Cox PH, but am concerned with the limitation of the continuous time requirement. In my dataset there are often ties. For example, out of 35000 records, ...
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14 views

Are there any possibilities to check model assumptions or any diagnostic for the proportional hazards model with correlated times?

As far as I know, regular proportional hazards model have assumptions that times have to be independent, hazards for each variables should be proportional and there should be noninformative censoring. ...
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26 views

Can proportional hazard regression predict the S(t) of subjects?

In my understanding, cox PH model can only give estimates of coeffs of regressors and then interpretations can be drawn. Since it does not assume a base hazard function, it cannot give an estimated ...
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33 views

Some doubts about survival analysis

I'm struggling to perform a correct and unbiased survival analysis, but I have some doubts. Data I observe a population of posts on a blog within a temporal window $[T_{0}, T_{final}]$. Each post ...
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51 views

Modelling proportional hazards in Cox Model using coxph in R

Assume I have a heterogeneous sample with two categorical variables A and B, each with 2 levels. Now I want to measure the effect of these on the survival function. So we assume proportional hazard, ...
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21 views

PH assumption: categorical variable (1 category does not interact with time)

After checking the PH assumption in STATA I found one variable (4 categories, 1=ref.) to interact with time (using 'tvc'). The 3th and 4th category had p-values <0.05. However, the 2nd category did ...
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how can I save the survival probability that used to calculate NRI for an indiviual?

I am trying to save the survival probability that used to calculate NRI (i.e. in the survIDINRI package) for an individual. and I wanted to use these probabilities to further analyse what kind of ...
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43 views

Cox model on bank customers

I am setting up a Cox model, to model the probability that new customers leave the bank . I had a nice set up, with plenty of significant explanatory variables, until the result of one categorical ...
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1answer
55 views

coxph R Squared Interpretation in R [duplicate]

A classmate and I have been looking over some stats regarding a study looking at the (lets call it) survival rate of an item of food. He ran his analysis using coxph to generate a model to compare the ...
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Cox/ Binomial Regression: How to reconcile Non-significant model with significant IVs

I'm been performing some survival and regression analyses corresponding to an event of interest being death or a certain surgical procedure, namely a shunt revision for pediatric neuro-surgical ...
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67 views

Setting up dataset for Cox regression with time-dependent variables

I posed a question about how to set up the code for this question here (SAS/proc phreg code) and @Fomite suggested that I pose a separate question about whether my data are set up correctly. ...
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51 views

SAS/proc phreg code

Background: I'm studying people seeking help. Participants described contacts with between 1 and 3 "responders" (e.g., friends, the police) in order- for example, a participant could have contacted ...
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55 views

Interpreting Cox & Binomial Regression: non-significant Chi-Square values w/ significant wald statistics

Scenario A: In Cox regression, the chi square analysis of the -2 log likelihood (or the omnibus in binomial) is not significant, but some of the values of the Wald statistic corresponding to some of ...
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30 views

How to interpret the overall model output of a Cox model?

I am running Cox regression analysis. I have read FOX's manual and I understand how to interpret the output of each predictor. But I am not sure how I should be interpreting the overall model output, ...
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Extended Cox model and cox.zph

I have previously had experience only with Cox PH model and its assumptions checking. Now for the first time I have my clients data with most of the covariates varying in time, only a few are fixed ...
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52 views

Survival Analysis Cox Ph Predict values

I'm coming with a question that I think is easy for most of you. But as I'm a newbie in Survival Analysis (I started 2 days ago), I can't figure out how to do it. I'm given a data set on ...
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14 views

ANOVA or AOV in R (cox ph)

I was wondering if you might be able to help me, I am doing a cox ph on some data – which looks at the effect of a poor diet (8x sugar) and the genotype (3 in total – 2 control, 1 experimental) on the ...
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Validate predictive power of Cox proportional hazards for individual observations

Note I've edited the example to be more intuitive and closer to my real data Intro I've got data on customers purchases and with it am trying to predict which customers are more likely to make next ...
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Difference between Cox Proportional Harzards Model and interval-based logistic model for survival regressions

I have a dataset of timestamped trader transactions (to the second). I want to conduct a survival analysis on the trades where a trade is started at startTime and ...
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12 views

Cox MSM or Recurring Event?

I have dataset containing clients' history of active and inactive periods (if there is any) up to present day. Also lots of info as time dependent covariates. I want to model this as MSM, where both ...
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Imposing follow-up time cutoffs on censored data for cox regression

When fitting cox regression models, is it valid to impose a cutoff for censored samples to have been followed for at least a given stretch of time for inclusion in the analysis?
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What model fit / predictive accuracy measure can be used to cross validate a Cox PH model with censored data?

How would you go about validating a Cox PH model with censored data? I am trying to run a Cox PH model on a dataset with observations that failed, and observations that are censored. Normally, I use ...
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Best packages for Cox models with time varying covariates

I am working on a project using Cox models with time varying covariates. My questions are: What are some good examples of conducting this analysis? What is the best R package to conduct this ...
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23 views

How can I make an ANCOVA in R (Prior to a Cox ph model)?

I want to make an ANCOVA analysis of the survival rate of flies after being on a bad diet for the first 21 days of their lives compared to those always on a normal diet. I have studied the responses ...
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Modelling credit risk by Ornstein Uhlenbeck process incorporating macro economic variable

I have a data set on default, application score and some macroeconomic variable, I want to model the next default as poison process whose parameter is itself random, it comes from an ornstein ...
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42 views

How to calculate adjusted HR?

What is the difference between crude HR and adjusted HR in Cox regression? How do we calculate adjusted HR?
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34 views

Can Cox models be used with time-varying covariates?

I work at a hard drive manufacturer. In my project, we have huge sets of testing data of hard drives. Most of them are time-varying covariates. My colleges are using cox regression. I doubt it. ...
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34 views

Cox regression with two dependent expanatory variables

I am doing a Cox regression to model how survival times of sick patients, after taking a certain number of pills. There are in total 10 different pills patients can ...
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scaled Schoenfeld residuals slope of regression line

If a regression line of scaled Schoenfeld residuals versus time (or log time) has a non-zero slope, proportionality is violated. However, what can we tell from the slope of the regression line? If it ...
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53 views

Schoenfeld residual independent of time?

I've seen it claimed (e.g. in these notes ) that "Schoenfeld residuals are, in principle, independent of time." Can this be right? Consider the following situation: You are using a Cox model to ...
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46 views

Age-matching for 2 samples in Cox Regression

I have 2 samples with a very significant mean age difference: Sample0: less-invasive,lower-risk surgery. mean age = 70. n=159 , deaths = 24 Sample1: higher-risk surgery. mean age = 60. n=86, deaths ...
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78 views

using caret and glmnet for variable selection

Im using the caret and glmnet package for variable selection. I only want to find the best model and the coefficients and use ...
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Interpretation of coefficients of glmnet - LASSO/Cox model?

I have done a LASSO / Cox model run for a large dataset of 10K observations which has 1200 Variables. ...