Survival analysis is concerned with modelling the time before subjects change state, typically time until death or failure. One key feature of such data is that they can be censored, that is, some subjects will not have changed state before the study ends.
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79 views
Testing survival against frequency of some event
I have the following data for 200 cases/subjects:
time to death over a 15 year period, $t$. A datum with a value of 180 months means that the subject did not die over the 15 year period.
the ...
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1answer
354 views
How to interpret the output of survival analysis?
I am beginner of survival analysis, so I am confused about some basic ideas in this area.
I think the basic assumption in survival analysis is that time of event for a subject can be estimated given ...
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2answers
148 views
Difference between survival analysis and classification?
Since the time variable can be treated as a normal feature in classification, why not using more powerful classification methods (such as, C4.5, SVM) to predict the occurrence of an event? Why lots of ...
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1answer
266 views
How to run survival analysis on big dataset?
I am recently involved in a project that needs to analyze the survival time of objects. Therefore, I plan to use the rms package to build a Cox model. The problem is, since the dataset I have is so ...
2
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2answers
702 views
Cumulative Incidence vs. Kaplan Meier to estimate probability of failure
To estimate the probability failure in medical sciences, it is not atypical to use 1-KM. However this does not account for competing risks, such as death by natural causes or causes unrelated with the ...
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1answer
272 views
Oddity in simulating Weibull survival times
Based on this guide to simulating survival times in SAS and R, I used the following code to generate two survival functions:
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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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57 views
Inferential methods on large panel data with sparse clusters and rare outcomes
Using longitudinal survey data on children using psychotropic medications, we are interested in estimating associations with medication classes, their persistence and adherence (longitudinal ...
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1answer
883 views
Difference between survdiff log-rank and coxph log-rank
I'm using the survival package in R to analyze clinical data. I am analyzing two different groups of patients, when I calculate survdiff in order to compare the curves, I got p= 0.135, but when I ...
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205 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 ...
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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 ...
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1answer
423 views
Cox regression - Hazard and Survival Estimates?
I have a couple questions about Cox survival regression:
1) Is it true that the hazard function h(t) is not available (even WITHOUT time dependent covariates)- and if not, is it because the baseline ...
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1answer
498 views
P-value of a survival ROC c-index
It is possible to calculate the c-index for time dependent outcomes (such as disease) using the survivalROC package in R. My question is : is it possible to produce a p-value for the c-index that is ...
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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) ...
4
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1answer
98 views
Time-wise treatment effect / survival analysis
Let's say I have some kind of survival data - i.e. I'm giving a drug that may cause mortality. So I have three patients: A, B and C. All are given the drug at Time t1.
Let's say patient A dies at ...
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242 views
Multiple imputation of time variables — which step to impute?
Lets assume I have a survival analysis study with an exposure, two covariates, and two time related variables. Say date of diagnosis and date of death. Combined, the two time related variables will be ...
2
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1answer
344 views
Floating Point Overflow while computing the Kaplan-Meier estimator in SAS
I try to estimate survival curves based on a Kaplan-Meier estimator using proc lifetest. However, SAS outputs an error message which I do not manage to circumvent. ...
2
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1answer
391 views
Martingale Residuals and Schoenfeld Residuals
If the Martingale Residuals indicate that a predictor $X$ violates the proportional hazards assumption but the Schoenfeld Residuals indicate that it does not....which one should you trust?
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2answers
229 views
Proportional hazards assumption meaning
Suppose we have a Cox-PH model and death is the outcome of interest. Suppose we have the predictors $X_1, X_2$ and $X_3$. Then does the PH assumption mean that for any person (i.e. arbitrary values of ...
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79 views
Problem with lagged covariates
Suppose we have a binary variable $X$ that indicates whether a person ate pizza during the week. This variable is recorded for an entire year. So we have $X_{1}, \dots, X_{52}$ values (1 or 0). ...
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1answer
258 views
How to generate a group summary categorical variable for survival analysis in Stata?
I have registry data for which I have data for individuals for each hospital attendance over a 10 year period. I wish to determine the effect of chronic antibiotic use upon acquisition of specific ...
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1answer
121 views
Survival analysis - help with determining source of error
I am trying to determine the effect of four interventions/exposures upon the acquisition of an infection (the interventions aimed at preventing the infection). I'm using registry data. My analysis ...
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1answer
814 views
How to perform a Wilcoxon signed rank test for survival data in R?
Say you have survival data like this:
...
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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 ...
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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 ...
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1answer
82 views
Best terminology to describe a time-series problem
I have a problem that I would like to investigate regarding time-series data, but as I'm inexperienced in the field of statistics, I am unsure of the best terminology to describe my problem (so I can ...
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91 views
Probability calculation in survival analysis
I have 13 similar independent units and I need to calculate the probability at least 6 of them to survive for time less than 1.10.
From a table with the Kaplan-Meir estimates I get the following;
...
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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 ...
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1answer
875 views
How to do cross-validation with a Cox proportional hazards model?
Suppose I have constructed a prediction model for the occurrence of a particular disease in one dataset (the model building dataset) and now want to check how well the model works in a new dataset ...
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371 views
Sample size and cross-validation methods for Cox regression predictive models
I have a question I would like to pose to the community. I have recently been asked to provide statistical analysis for a tumor marker prognostic study. I have primarily used these two references to ...
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1answer
1k views
Different prediction plot from survival coxph and rms cph
I've created my own slightly enhanced version of the termplot that I use in this example, you can find it here. I've previously posted on SO but the more I think about it I believe that this probably ...
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253 views
What data structure is necessary for survival analysis?
I'm relatively new to survival analysis and try to get my data in the right shape.
I have two tables both concerning the observed individuals. If I just would use one of the tables, I would have ...
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1answer
175 views
What statistic test apply to a cell count time line?
I am a PhD student with some difficulties about what test to choose to verify an experiment. Hope you can give me some help!
My experiment:
I am counting the number of a subset of cells in Drosophila ...
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3answers
217 views
Survival analysis with categorical variable
I have event time data for subjects with different categories (A, B, C etc.) yearly observed. To my understanding my data is both right and interval censored (?).
Subjects' category can change from ...
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1answer
293 views
Predicting the time until an expected event occurs
I have a situation where an event is supposed to occur every x minutes for a number of different sites (each site could be configured for a different time interval x). From time to time the event may ...
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1answer
146 views
Compare survival of one population to the general population
I have the survival dataset of a population with a special disease. I´d like to compare this population with the general population to see whether this population has a decreased life-expectancy ...
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1answer
97 views
Inconsistency of the Breslow estimator
The Breslow estimate is commonly used in the Cox proportional hazards model. However this paper by Deborah Burr
Burr, D. (1994). On Inconsistency of Breslow's Estimator as an
Estimator of the ...
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0answers
133 views
Variance of the Kaplan-Meier estimate for dependent observations
Can someone help me find a way to estimate the variance of the Kaplan-Meier estimate with dependent observations? Specifically, I have failure time data from patients with several different ...
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1answer
133 views
Are survivor functions meaningful with proportional hazards models?
Does the survivor function estimated after running a Proportional Hazards model give valid predicted probabilities of an event happening after a number of time periods?
The only source I've found on ...
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3answers
198 views
Understanding survival at time function
This question is related to a few others (Here,Here) on the topic as I have been searching for information. Hopefully this one is sufficient.
1) I am seeing differences in the relationship between ...
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1answer
274 views
How can I censor entries at failure or an exit age in STATA?
I am attempting to construct a survival analysis in STATA whereby subjects fail if the failure condition is met (Staph) but are also removed from the model once they are over 1100 days old. My ...
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1answer
255 views
How can I display a survival curve with right censoring marks?
I have the following survival data and have constructed a survival plot however cannot mark the right censored points (which makes me think my survival graph is also incorrect) - how can I manage this ...
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2answers
224 views
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1answer
191 views
How do you plot survival functions for specific values of covariates in SAS?
Suppose I do the following:
proc phreg data = new;
model time*censor(0) = x y;
run;
Also suppose $x$ is a binary variable and $y$ is a ...
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1answer
398 views
SAS Code for Survival Analysis
In PROC PHREG, how do you set a continuous variable at a certain value as the reference level? For example, suppose x = 3.5, 3.6, 4.3, 5.4 and we want x = 6 to be the reference level. How would you do ...
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1answer
249 views
Proportional hazards assumption
The proportional hazards assumption basically says that the hazard rate does not vary with time. That is, $\text{HR}(t) \equiv \text{HR}$. When can we assume this? What if the hazard ratios at ...
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3answers
917 views
Finding median survival time from survival function
Is the best way to find the median survival time from a survival plot just to draw a horizontal line from $p = 0.5$ to the curve and project down to the x-axis?
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2answers
2k views
Time dependent coefficients in R - how to do it?
Update: Sorry for another update but I've found some possible solutions with fractional polynomials and the competing risk-package that I need some help with.
The problem
I can't find an easy way ...
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1answer
196 views
Sampling distribution is skewed in a fully Bayesian inference of MCMC in Cox PH models
I used the MCMC method to estimate linear models with a fully Bayesian inference previously, and had no problem from estimated coefficients. Recently I use the same way in a semiparametric Cox PH ...
