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

learn more… | top users | synonyms (1)

0
votes
2answers
21 views

Cox regression covariate specific concordance independent of distribution of covariates in sample?

Concordance seems to be a very good metric for telling you how well the model allows you to order individuals for the particular sample that is being used. However, when applying a cox regression ...
0
votes
1answer
8 views

Variance estimator of quadratic term of Cox PH model

I have a failure time data set. I want to fit Cox PH model with quadratic term like $h(t;x)=h_0(t)*exp(x\beta_0+x^2\beta_1)$ What will be the mathematical formula for variance of quadratic term? ...
0
votes
1answer
36 views

Can I use Cox Regression here?

I have a data-set where I want to do a regression of survival probability given amount of drug injected into a subject. The more drug injected, the less likely the subject will survive after say, 3 ...
0
votes
1answer
45 views

R function survfit(): give newdata reference values for factors with >2 levels?

The goal is to plot separate survival curves for each level of a categorical variable in R, using a coxph model including the variable and a second categorical variable with >2 levels. If the second ...
1
vote
1answer
21 views

Different output for cox regression in R vs SPSS

During my analysis that I perform with a collaborator we get consistently different ouputs in cox regression between R and SPSS. Betas and p-values differ minutely, usually somewhere in the third or ...
1
vote
0answers
21 views

Handling Informative Censoring in Survival Analysis

In a survival study with informative censoring (for example, studying the effects of cigarettes on mortality and smokers are more likely to be Lost to Follow Up). This causes the censored data to be ...
1
vote
1answer
31 views

Time-dependent variable in survival analysis using R

I am conducting a retrospective study where I have a cohort of cases who underwent the same surgical procedure. The primary outcome of the study is the recurrence incidence rate during a follow up ...
0
votes
0answers
22 views

Computing hazard ratio between groups adjusting for other confounding variables

I have groups formed based on BMI; consider the standard Underweight, Normal, Overweight, etc. groupings for BMI as you might see for classification. I'd like to form a hazard ratio for comparing any ...
2
votes
1answer
43 views

Consequences of violating proportional hazards assumption in Cox model

What are the consequences of violating the Proportional Hazards assumption in a Cox Model? I've got a Model where two factors are highly significative, but all the estimated betas associated to the ...
1
vote
0answers
14 views

Cox PH model set up when some variables only measured occasionally

I am working on an analysis of observational data over 16 years. I'm attempting to conduct a Cox proportional hazards regression but am not sure my data set is in the correct format. I have about 10 ...
0
votes
1answer
27 views

Extrapolate an Extended Cox model from 6 years to 30 without assuming a parametric distribution in R

I am attempting to extrapolate a Extended Cox Model (cox model with a time-varying covariate) from 6 years to 30 years in R. Is there a way to do this? I have thought of a mediocre way of doing this: ...
0
votes
0answers
16 views

Cox Regression Hazard Ratio in Percentiles

I computed a Cox proportional hazards regression in R. cox.model <- coxph(Surv(time, dead) ~ A + B + C + X, data = df) Now, I got the hazard ratio (HR, or ...
0
votes
1answer
29 views

Vectorized Implementation of Cox PH Model Scoring Process

I created a Cox Survival model and for my purpose I need to use the mean instead of the median. In order to test the results of the model, I need to calculate a mean prediction for every record in my ...
0
votes
2answers
52 views

How to change baseline patient in Predict function in rms package in R?

I am doing a time dependent Cox model using cph function in rms package. I use Predict and plot.Predict to plot the hazard ratio on y axis and a continuous covariate (e.g. LDL cholesterol) on X axis ...
0
votes
0answers
5 views

How to determine covariates that predict presence of a disease at a certain age?

I'm familiar with survival analysis. I was asked to find variables that predict being free from hypertension (ie having normal blood pressure) at age 50. Data is longitudinal with repeated ...
0
votes
0answers
7 views

Failure time events with escalating severity

I have participants (in a randomized clinical trial) who are not merely failing therapy by experiencing the clinical outcome, but are also escalating to a more severe clinical state. I'm looking for ...
3
votes
0answers
26 views

How is the hazard ratio in Cox proportional hazard models affected by the case sampling?

I'm trying to conduct survival analysis using Cox proportional hazard models, looking at a biomarker for heart disease. Age is a major risk factor, so I'm modeling the age as the time scale (counting ...
0
votes
0answers
15 views

Comparing influence of coefficents in cox regression (conditional logit)

I am estimating a discrete choice model (conditional logit) with the help of cox regression in SPSS. I would like to asses which of my coefficients has a greater impact on the model. So I ran a ...
1
vote
1answer
35 views

Why is coxph() so fast for survival analysis on big data?

I frequently do survival analysis on large data sets. One million samples or more is typical, and this seems to be much more than typical research usage. Many algorithms I've used are prohibitively ...
2
votes
0answers
42 views

Why is the derivative not zero?

I am working with survival models and I am using R's coxph function to learn the Cox proportional hazard model. To try it out, I am using the standard veteran dataset (obtainable by loading the ...
2
votes
0answers
44 views

Time-dependent coxph output and making predictions in R

I'm trying to use a Cox proportional hazard model to predict the time until an employee terminates from an organization. There are a bunch of covariates (~20), some of them time-dependent. So I've ...
0
votes
0answers
11 views

Point process models

Two of the popular models for analyzing point process data are Cox and Hawkes processes. My question is how do we compare the statistical properties of these two processes as they both can be ...
0
votes
0answers
19 views

Exp(b) in multivariate Cox regression

I am trying to interpret the results of a Cox regression. I ran a multiple Cox regression analysis of an categorical variable—heart rate including 5 levels. I added covariates that were also ...
4
votes
1answer
117 views

How to visualize a significant interaction between two linear predictors using the rms package?

Two linear predictors interact significantly (see below). How can I visualize this interaction in a plot? ...
0
votes
0answers
34 views

Different quantile values for a predictor between the root data and and the data of a Predict() object

I want to plot a continous predictor using restricted cubic splines and indicating the distribution of the linear predictor using a box-and-whisker plot. However, the quantile values differ from those ...
0
votes
0answers
9 views

Cox model with known measurement error

I am trying to perform a univariate Cox PH survival analysis in R. My covariate was generated from another analysis, meaning that I have a 95% CI range (between 0 and 1) for the values. Right now, I ...
0
votes
1answer
42 views

Comparing regression models with different coding of the same linear predictor

How can I determine whether one coding of a linear predictor leads to a better fit of the corresponding regression model than the other? In the following example, the restricted cubic spline coding of ...
0
votes
0answers
22 views

Cox Time Series Data — Analysis of Interaction Terms

In a time series data set using Cox Proporational Hazard Rate, I am testing a model with interaction terms. I am worried that my interaction term is biased by several specifications of my model and I ...
4
votes
2answers
166 views

Comparing a linear model with a spline model

I try to figure out how to describe my continuous variable. Unfortunately, I did not understand all of the statistics. I would really appreciate I you guys would help me out here. To better illustrate ...
1
vote
0answers
22 views

Cox survival analysis versus multilevel modeling

I'm debating the wisdom of a couple different approaches. I am constructing a model that measures whether the amount of a treatment received leads to a person coming back for another treatment or ...
0
votes
1answer
43 views

Difference between multi-factor ANOVA and Cox proportional hazard model?

I am wondering what is the difference between multi-factor ANOVA and Cox proportional hazard model? As I understood both of them test the significance of some independent factors on a dependent ...
0
votes
0answers
65 views

How to simulate informative censoring in a Cox PH model?

I wish to simulate events from a Cox PH model where the censoring is informative, and to compare parameter estimator quality with estimates obtained from data generated by a Cox PH model with ...
0
votes
1answer
61 views

Interpretation Interaction in Cox Regression

I am estimating a discrete choice model with the help of cox regression in SPSS. I would like to interact two continuous predicting variables. The main effect of one of the ineracting variables is ...
0
votes
0answers
16 views

What are easy steps of finding cutpoint in continuous variable with Time to event outcome, in Stata?

I find it painful to manually guess a dichotomized cutpoint predictor (continuous) for an time to event outcome in Simple Cox proportional hazard model. Currently I was trying to find the cutpoint ...
1
vote
0answers
16 views

Very puzzling - naming the endpoint of survival analysis

A question that should be straightforward for statisticians but is puzzling me to the point I am nervous. I am doing a PhD in Epidemiology and am going to use Cox regression. The predictor is a ...
1
vote
1answer
72 views

Analyzing seasonality in data

In order to analyze the data in presence of seasonality, I used two methods: Proportional hazard model (Cox model) and time series method (Triple Exponential Smoothing (Holt Winters Method)). Now , my ...
0
votes
0answers
18 views

Comparing Cox models

We want to compare different methods of modelling a continuous covariate (X) in a Cox model. For example, in the first model we use X in its continuous form. In a second model we categorize X into ...
0
votes
0answers
23 views

bias of an estimator when the variable is categorical

I want to calculate the bias of the coefficient estimate (beta hat) in Cox regression. But for a categorized variable, for example using quantiles we define a variable with 4 categories, then the ...
2
votes
1answer
63 views

Get survival rates from a cox regression in R

I am fairly new to survival analysis and am playing around in R. I have a fairly simple cox model ...
2
votes
1answer
192 views

Univariate cox regression hazard ratio in SPSS

I'm currently doing some analysis for a retrospective cohort study of biomarkers in cancer patients. I've noticed that some papers have utilized univariate cox regression analysis to generate a hazard ...
1
vote
0answers
26 views

Parameter estimates from extended cox model using the coxph() function from the survival package in R

I want to understand how the parameters from a Cox Model using the coxph() function from the survival package in R are estimated. I am following a book by Rizopoulos [1]. In the book the partial log ...
1
vote
0answers
16 views

covariate-adjusted analysis for time to event endpoint in a cross over design RCT

I have a time to event endpoint in a 2x2 crossover RCT which I would like to analyse with a regression model to adjust for covariate effects. I am supposing I cannot fit a Cox proportional Hazards ...
0
votes
1answer
32 views

Risk ratios in a Cox hazard model

I'm reading a paper which gives "Risk ratios from Cox hazard models with time-varying covariates". Time-varying covariates just means that, for example if $X_i$ is a covariate for person $i$ then it ...
4
votes
1answer
102 views

Post-hoc power size calculation

I have, probably, a simple problem. I've finished analysing the results of an observational prospective study conducted in our unit. In this study I evaluated if a specific biomarker is independently ...
0
votes
0answers
31 views

How to interpret the R output of anova.coxph

The likelihood ratio chi^2 test is the gold standard for comparing nested Cox models. However I am not sure how to interpret the R output. ...
4
votes
0answers
51 views

Time varying coefficient in cox model

I have a model for survival after an injury that is borderline passing the Schoenfeld test for the proportional hazards assumption (cox.zph() in R). However, ...
1
vote
0answers
29 views

How to do Cox regression if we have a variable which violates an assumption?

Is there a better way than stratification to do Cox regression for two variables, one qualitative and other quantitative, the qualitative (and more important one) violates an assumption of Cox ...
2
votes
1answer
45 views

Cox Regression: Testing for effect in subgroup

I'm using a cox proportional hazard model in R to see if a treatment variable (treatment or placebo) has effect on the survivaltime of patients. I intend to test this for each of my grouping variables ...
0
votes
1answer
26 views

Simple Cox-related question regarding the LR test

I'm writing the Results section of a paper: If the LR-test for a Cox proportional hazards model is not significant, but one of the predictors is significant, does one (usually) report the covariate's ...
0
votes
0answers
25 views

Predict Kaplan-Meier Curve from Hazard Ratios

For illustration purposes I want to plot some potential hazard ratios, based on a known proportional hazard model. For example, plot the known curve, then plot what the curve may look like with HR's ...