The Cox model refers to a method of survival analysis. Its great advantage is that it does not require specification of the hazard function on time.
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32 views
extended cox model with continuous time dependent covariate - how to structure data?
I need to run an extended cox model with a time-varying covariate in R: let’s call it the number of doses (X). I am interested in the hazard ratio associated with each level of X, ie. how an ...
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0answers
22 views
How to interpret the frailty terms in a coxph.penal model?
I have the following coxph model:
Surv(Y) ~ genotype + treatment + age + frailty(batch) + genotype:frailty(batch)
...
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1answer
89 views
Simulation Analysis of a Cox Survival Model with Change Point.
I wish to simulate survival data for the following probabilistic model which will be analyzed using a Cox model:
An exposure $X$ is modeled as binary having $X \sim_{iid} \mbox{Bernoulli}(p)$ where ...
3
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3answers
313 views
Cox model vs logistic regression
Let's say we are given the following problem:
Predict which clients are most likely to stop buying in our shop in next 3 months.
For each client we know the month when one started to buy in our ...
0
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2answers
84 views
Should I keep the interaction term?
I am doing research on mortality. I am running cox regression and I am adjusting for 40 variables which are proven in the literature to be related with mortality. My main exposure is X. In my final ...
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0answers
84 views
How do I perform a cox regression analysis while adjusting for a variable?
I would like to perform a multi-variate cox regression model looking at various factors influencing the risk of recurrence of disease such as BMI, age, year of surgery, etc. Some of these patients ...
1
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1answer
93 views
Backward selection in a Cox regression model
My goal is to fit a cox regression model in SAS, for which I use the PROC PHREG statement. As I am still new to regression methods, I would appreciate a little of ...
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0answers
48 views
Can you use Cox regression for more than just modeling time to event data?
Can you use Cox regression as a general regression modeling choice not just for modeling time to event data? That is, couldn’t you use a Cox regression to model any (positive) ordinal/interval ...
3
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2answers
206 views
In Stata, why do the stcox CI differ when using margins?
I'm trying to understand how the margins and marginsplot work after stcox command in Stata.
...
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0answers
102 views
probit tobit model
I am using a dataset with approx 2000 obs to look at the effect of a number of covariates on:
whether a person is unemployed or not (binary)
the period of time a person has been unemployed (Q ...
2
votes
1answer
58 views
Which model should I use if I get different models using forward and backward Cox regression?
I am running an Cox regression with my data. In my final model I had four potential predictors and did first a forward (Wald method) Cox regression and then for validation of my model a backward (Wald ...
1
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2answers
171 views
Computing c-index for an external validation of a Cox PH model with R
First off, I'll state that I'm aware many questions get asked about the c-index. I've searched this site and others, and I haven't found an answer for my situation. I can successfully use ...
2
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0answers
111 views
LASSO vs AIC for feature selection with the Cox model
I have some questions about the Lasso.
After using the AIC or BIC to select a model, the model is fit with the variables selected in order to get the standard errors of the estimates with CIs, ...
2
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2answers
57 views
Can you use proportions as a covariate in a Cox proportional hazards model?
In R's survival::coxph function, can I mix a covariate representing proportions (in the range 0.0-0.5) with an integer covariate (in the range 1-15), or should I ...
8
votes
2answers
246 views
Propensity score weighting in Cox PH analysis and covariate selection
Regarding propensity score weighting (IPTW) when doing Cox proportional hazard modeling of time-to-event survival data:
I have prospective registry data where we're interested in looking at treatment ...
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0answers
48 views
Using propensity scores from twang in coxph
I've used the twang package to calculate propensity score weights in my observational data set. The twang vignette uses the ...
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0answers
69 views
Interval censored current status data Cox proportional hazards model in R
Given interval censored survival times, how do I perform a current status data (case1 interval censored survival time) Cox PH model in R? I found the R package intocox, but the output is not ...
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0answers
104 views
Bootstrap randomized Lasso selection for a Cox model
I'm interested in variable selection for a cox proportional hazards model.
I've read this article which slightly favours randomized bootstrap lasso selection over bootstrap lasso selection since it ...
7
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1answer
195 views
Using multiple imputation for Cox proportional hazards, then validating with rms package?
I've been researching the mice package, and I haven't yet discovered a way to use the multiple imputations to make a Cox model, then validate that model with the rms package's ...
5
votes
1answer
327 views
EM algorithm R code on Cox PH model with frailty
Let say I have a 'kidney catheter' data set. Data are about the recurrence times to infection, at the point of insertion of the catheter, for kidney patients using portable dialysis equipment. ...
1
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2answers
160 views
Interpreting Cox regression
My regression results are as follows.
Variable B exp(B)
age 0.004575 1.004586
capital 0.2250 1.2524
year -0.1026 0.9024
...
1
vote
1answer
194 views
Best predictive Cox regression model using c-index and cross-validation
I want to explain the problem I have in this moment to know what do you think about the implementation I am designing.
I have a set of 40 genes expression data as binary variables (overexpressed yes ...
1
vote
1answer
113 views
Permutation test for the significance of several dependent regression coefficients from separate models
I have $i>100$ Cox regression models which differ only in one explanatory variable, $x_i$. They have the same outcome data and the same other explanatory (adjustment) variables.
I want to control ...
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0answers
44 views
Improving accuracy of Cox model
I am trying to improve the accuracy of a Cox model I am using to predict the length of stay of children in foster care. I am measuring the AUC under ROC, where each ROC corresponds to a fixed value of ...
1
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1answer
193 views
Comparison of Cox models
I am new to statistics and SPSS v 20. I am doing survival analysis - KM and Cox regression with SPSS. I am trying to make Cox models with different variables - clinical, genetic etc. I am interested ...
7
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5answers
1k views
Prediction in Cox regression
I am doing a multivariate Cox regression, I have my significant independent variables and beta values. The model fits to my data very well.
Now, I would like to use my model and predict the survival ...
0
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0answers
82 views
How to count variables in Cox PH model?
I am doing Cox PHR and I have several categorical, ordinal and continuous variables. Now we did univariate analyses (Log-Rank test) categorizing each continuous variable into 2 categories (based on ...
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2answers
400 views
Cox-regression model: question about acceptability, meaning, & reporting
Apologize for insufficient info in my previous version of this question. So, I am comparing patient survival in a retrospective study between two different groups, using SPSS. Now the difference came ...
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0answers
28 views
What to report and how to report Cox-regression survival analysis in a research paper [closed]
I am a medical graduate trying to analyze large data and write a paper about it. Can any one explain what should I included in the article about the Cox-regression model.
HJP
2
votes
1answer
189 views
Schoenfeld residuals
In a Cox proportional hazards model with many variables, if the Schoenfeld residuals are not flat for one of the variables, does this invalidate the entire model or can just the poorly-performing ...
5
votes
0answers
154 views
What are the options in proportional hazard regression model when Schoenfeld residuals are not good?
I am doing a Cox proportional hazards regression in R using coxph, which includes many variables. The Martingale residuals look great, and the Schoenfeld residuals ...
2
votes
0answers
94 views
How are absolute risks estimated by the cox model?
According to my modest understanding, the cox model is all about estimating hazard ratios, relative measures of risk.
However, it is possible (in R using e.g. the packages pec or peperr) to estimate ...
6
votes
1answer
135 views
How important is using the exact method for ties in a Cox model, and how long should this take?
I'm analyzing the results of some simulation work using a Cox proportional hazard model, and I have what I perceive are a great many ties in the data, representing when a particular individual in the ...
6
votes
1answer
1k views
Cox proportional hazard model and interpretation of coefficients when higher case interaction is involved
Here is the summary-output of the Coxph-model I used (I used R and the output is based on the best final model i.e. all significant explanatory variables and their interactions are included):
...
1
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1answer
220 views
How important is it to transform variable for Cox Proportional Hazards?
I am building a Cox PH model for recurrence-free survival from breast cancer. One of my variables, the number of involved lymph nodes, is highly skewed with many more "0" values than positive ...
5
votes
1answer
401 views
What is the “$R^2$” value given in the summary of a coxph model in R
What is the $R^2$ value given in the summary of a coxph model in R?
For example,
Rsquare= 0.186 (max possible= 0.991 )
I foolishly included it a manuscript as ...
1
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0answers
246 views
Segmented time-dependent covariate
I'm performing the cox regression analysis, where I have the model with 1 time-independent (treatment (yes/no)) and 1 time-dependent predictor (blood pressure level).
Outcome is death (yes/no). Time ...
2
votes
2answers
199 views
Cox model with missing covariates
I was wondering if any of you have experience in fitting a Cox model to data with missing covariates. Do you know of any reference addressing the issues associated with Cox regression with missing ...
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1answer
159 views
cox proportional hazard model
am doing my dissertation involving cox model and i would like to understand how you interpret the survival table at mean of covariates. how i do u i determine the survival function from the output
...
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0answers
206 views
Comparing Hazard Rate Ratios for different outcomes on the same sample
Suppose I have survival data coming from a cohort study. The outcome of interest is death and a subject can die either because of cancer or because of other causes. The two outcomes under study are ...
1
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3answers
191 views
Critical appraisal of survival paper
I must make a critical appraisal of a cancer survival paper. I hope someone here can give some hints. The paper investigates person-level markers of socio-economic status as exposure and looks for ...
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2answers
202 views
What is the difference between a hazard ratio and the e^coef of a Cox equation?
As I understand it, the definition of the hazard ratio is the ratio of two hazard rates. Often the exp(coef) from a Cox model is also used as an estimate of the hazard ratio. These methods give two ...
2
votes
1answer
185 views
How to choose the best of two highly correlated predictors in cox proportional hazards regression
I have built a good model of time-to-stroke under cox ph assumptions using a predictor of stroke risk (Framingham risk score). It incorporates a score according to Age, Gender, controlled / ...
3
votes
2answers
1k views
How to calculate predicted hazard rates from a Cox PH model?
I have the following Cox PH model
(Time, Event) ~ X + Y + Z
I would like to get the predicted hazard rates (i am talking about hazard rates NOT hazard ratios) ...
5
votes
1answer
2k views
Interpretation and validation of a Cox proportional hazards regression model using R in plain English
Can someone explain my Cox model to me in plain English? I fitted the following Cox regression model to all of my data using the cph function. My data are saved in an object called "Data". The ...
5
votes
2answers
372 views
Cox proportional hazard model and non-randomly selected sample
Are there any methods to correct bias in Cox proportional hazard model caused by non-randomly selected sample (something like Heckman's correction)?
Background:
Lets say the situation looks as ...
4
votes
1answer
259 views
Robust variance/covariance matrix in Poisson regression
Suppose I have survival data with more than one row per subject, because I have splitted the follow-up time of each subject into pieces (maybe because I have one or more time-varying variables or ...
2
votes
1answer
320 views
Stratified Cox model
I am working on fitting a Cox model to predict. But several predictors violated the proportional hazards assumption. I am gonna to do stratified Cox model to adjust them. But the results of stratified ...
1
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0answers
100 views
Cox model with Lasso for PH test and P value
I am using the penalized package in r for fitting a Cox model with a lasso penalty.
Does the Cox model + lasso need to test proportionality?
How do you get the ...
2
votes
1answer
417 views
Discrimination and calibration of Cox model
I have been working on fitting Cox model for prediction by using the rms package. I want to measure model calibration and discrimination.
Discrimination was measured by using ...
