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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Finding significant predictors of psychiatric readmissions

The set of data I am working contains nearly 17,000 independent spells (each spell consists of a number of hospital episodes) each belonging to a unique patient ID. I have spent a very long time ...
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How to tell the probability of failure if there were no failures?

I was wondering if there is a way to tell the probability of something failing (a product) if we have 100,000 products in the field for 1 year and with no failures? What is the probability that one of ...
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13 views

survival mixture model of gamma distribution via EM algorithm

I generated survival data for a three component survival mixture of gamma distribution with random right censored observations in R with the code; ...
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26 views

How to show that the cumulative hazard function is equal to the formula below?

I need help to show the equation below. $$H(t)=ln[\frac{mrl(t)}{mrl(0)}]+\int_{0}^{t}\frac{1}{mrl(u)}du$$ where mrl is the mean residual life using $$h(t)=\frac{\frac{d}{dt}mrl(t)+1}{mrl(t)}$$
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14 views

Stratified concordance index (survival::survConcordance)

What is the idea of having a stratified concordance (C-index) in survival::survConcordance, as opposed to computing the concordance over all samples ignoring the strata? Can there be some inflation ...
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15 views

For the survival analysis package in R, what is the log-likelihood of “survreg( Surv(time, censor) ~ age, dist=”exponential“)”?

I am currently trying to read through examples from http://www.ats.ucla.edu/stat/r/examples/asa/asa_ch1_r.htm. One of the models I saw was: ...
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42 views

ML estimate of exponential distribution (with censored data)

In Survival Analysis, you assume the survival time of a r.v. $X_i$ to be exponentially distributed. Considering now that I have $x_1,\dots,x_n$ "outcomes" of i.i.d r.v.'s $X_i$. Only some proportion ...
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36 views

Application of Survival Analysis

The question is whether prenatal diagnosis of a congenital condition shortens the time to surgical intervention. The condition is one that is obvious at birth, but not necessarily in utero, and once ...
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68 views

How to calculate probabilities when there is censoring?

Suppose we have 10 patients among whom 4 readmit and 2 get censored. Then what is the probability of readmission of these patients? My intuition tells me it should be 0.5, because I couldn't observe ...
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9 views

Is the magnitude of the hazard ratio change reflective of survival function change?

I need to know the change in survival caused by increasing inbreeding in my study group. As my model has random effects, and as coxme has no easy ...
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1answer
42 views

Interpreting output of Cox regression model

I am trying to use two variables - activity score (ascore - a whole number indicating amount of activity) and gini (given by Gini-Simpson index - a value ranging between 0 and 1, indicating diversity ...
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30 views

How can the output from a Cox proportional hazards model be mathematically translated into a log regression model? [closed]

I would like to write down the log-regression model associated with the formula: coxph(Surv(time, status) ~ rx + cluster(litter), rats) I am not interested in ...
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38 views

Study design - fresh look!

Need to be advised outside of the circle. I am more a physiologist+mathematician plus-c,c++,java coder/developer. Chart data. From year 2001 till 2012. 89 nursing stations or emergency call ...
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1answer
42 views

Expected survival time from log-logistic survival model in R from survreg

I'm currently estimating a survival model (accelerated failure time model) with a log-logistic distribution in R using the survival package and the survreg function. I want to simulate expected ...
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35 views

Estimating mortality rates with direct age-standardization

I'm attempting to calculate the mortality rates of AMI (acute myocardial infarction) in patients (cases) with high bloodpressure, between the years 2001 to 2008. For every case I have 2 matched ...
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146 views

Modelling mortality rates using Poisson regression

I'm examining trends (between 1998 and 2011) in mortality rates among patients with Crohn's disease. Each patient (case) have been included during 1998 to 2011. At inclusion, each patient have been ...
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1answer
15 views

Is there any repository with interval censored time-to-event datasets?

I'm looking for this particular structure of data for working on my thesis. In particular, I need interval censored with a cure fraction data. This kind is actually popular in medicine and clinical ...
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1answer
26 views

What Grouping Method To Determine Average Over Lifetime?

I have the following data: When individual 'x' joined a company. As the data is limited to 2 years I do not know the start date of every individual. When individual 'x' left the same company. If this ...
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2answers
96 views

How to make prediction in survival analysis using R?

I have fitted a survival model in R which is below. However, I am not sure how to make predictions. I tried predicting the survival probability that a patient whose design matrix is ...
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22 views

How to compare repeated measurements among groups with non-normal data?

I want to investigate differences in two variables among 3 groups. The variables are "% of time active" and "latency to exit a cage", and each group corresponds to a different context (the focal ...
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18 views

Confidence interval before the first event in a Kaplan–Meier curve

The confidence intervals for Kaplan–Meier curves in survival analysis only exist for times after the first (non-censored) event. Example R code: ...
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1answer
79 views

Is oversampling done for Cox regression data?

I have a dataset consisting of about 48000 people, about 40,000 of which die before the end of the study and get a failed = 1 and the remaining 8000 have a failed = 0 because they're either lost to ...
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47 views

Model selection using AIC in Survival Analysis

As far as I know, the model with lowest AIC is said to be better. However, according to the R output below, the writer says, the model called wei is better, whose ...
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1answer
80 views

Why are the signs of my coefficients are different?

My code is: library(survival) attach(veteran) survreg(Surv(time,status)~karno+diagtime+age+prior+trt ,dist="w") My analysis and the one in a book are as follows: ...
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1answer
52 views

How to interpret a status other than alive or dead in data for survival analysis?

I am working on a famous data set from this book. The data set consists of measurements on 418 patients. I am interested on modelling the variable; futime: number of days between registration ...
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119 views

Cox discrete time regression model question

Cox's 1972 publication Regression Models and Life Tables links logistic regression to an extension of the discrete time proportional hazard model. I do not understand how Equation (21) in the ...
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16 views

Is it possible to gain point survival estimates from a coxme object?

I have a coxme object: (Age, status) ~ F + X1 + X2 + (1|R1) + (1|R2) + (1|R3) Where F is an individual's level of inbreeding, X1 ...
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61 views

Model Selection with Competing risks in Cox regression

When doing cox proportional hazards regression one often has competing risks. The typical approach for this is to fit separate cox proportional hazards models for each risk, censoring the competing ...
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1answer
42 views

R adds unexpected variable to interaction model

Not sure if this is more of a programming question (in which case please move to stack overflow) or a statistical model question (in which case, please read on!) I'm exploring a data set and doing ...
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1answer
26 views

Study Length Over-Estimating Hazard Ratio?

Are cox model studies over too long a time-scale at risk of over estimating (or under estimating) a covariate's effect on hazard? I'm studying inbreeding in a captive animal population. Some ...
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45 views

Survival analysis with competing risks

I am analysing the effect of an intervention to reduce length of hospital stay (LOHS) after surgery. The main outcome is LOHS and the intervention is the main exposure. Death while in hospital is an ...
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1answer
72 views

Comparison of predictive models

I am trying to compare the predictive ability of various models in predicting survival in patients. I would like to examine the predictive performance of each model using 4 tests: squared Pearson ...
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32 views

What does muhaz return?

A pretty basic question. I have read somewhere that the muhaz function in muhaz package will return the baseline hazard rate for COX model. The muhaz document states that it "Estimates the hazard ...
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Survival analysis for matched set cohort data - Methods for absolute and relative risks?

BACKGROUND I have a matched data set with 10,000 cases and 20,000 controls. Cases are defined as such due to a diagnosis of COPD (Chronic Obstructive Pulmonary Disease - a lung disease caused by ...
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Survival Analysis on Telecom Churn in R

I am working on Telecom Churn problem and here is my dataset. http://www.sgi.com/tech/mlc/db/churn.data Names - http://www.sgi.com/tech/mlc/db/churn.names I'm new to survival analysis.Given the ...
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41 views

Estimating mortality using Cox model with baseline

I have been reading online notes and papers on how to build survival models using CPH, and I think I've a good idea how things work. However, there are two questions I still have in mind: 1) let's ...
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27 views

Dealing with non events in one treatment group - survival analysis

I am currently trying to apply survival analysis to several tree species which were monitored for growth and phenology for 4 years and seperated into three treatment groups. From this data I have ...
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2answers
101 views

How to calculate the HR and 95%CI using the log-rank test in R?

The R survival package is very useful to do survival analysis. And I know the survdiff function can be used to compare the difference of survival time in two or more groups. And the p-value number can ...
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What is the survival function for a Weibull model with one covariate?

What is the survival function for a Weibull model with one covariate? I can find the survival function for a model with an intercept only, but I'm having trouble finding how to find the survival ...
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30 views

Multivariate survival with recurrent events and spikes back to 100% alive

I am trying to solve for what seems to be a multivariate survival model, but am getting stuck as there are both recurrent events and also jumps back to 100% alive. Rephrasing the larger project in ...
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81 views

Prediction with categorical variables in Cox regression

I'm doing survival analysis with Cox PH. I have my final model based on averaged models and I have four categorical variables with multiple levels each. I computed the fitted values using ...
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23 views

Evaluating survival models in the presence of covariate-dependent censoring

I have a censored survival analysis problem with the following characteristics: Failure times are discretized The censorship distribution depends on certain covariates I don't have a ...
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1answer
55 views

Using random forest for survival analysis with time varying covariates

I've been trying to train a model that predicts an individual's survival time. My training set is an unbalanced panel; it has multiple observations per individual and thus time varying covariates. ...
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74 views

Cox Models treatments depending on time until event

I'm trying to get the "productivity" of treatments like sending an email, calling or sending an SMS and their combinations in the paying debtor's probability. I couldn't find one model that satisfies ...
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1answer
162 views

Violation of Cox Proportional Hazards by a continuous variable

[This question is related to 1 and 2 on this site.] I fit a Cox model with these three time dependent variables: {s:numeric, C:binary, l:numeric }. I have 1069 ...
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Censored data from a truncated distribution (Stan)

I'm trying to write a survival model of fossil species durations. In this case, the minimal possible duration for a species is 1. Also, the general idea in paleontology is that we are only observing a ...
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42 views

Akaike information criterion for Cox proportional hazard models

I am conducting an analysis of survival data using Cox proportional hazard (CPH) models, to figure out what is the best model to use. The models I am comparing are non-nested. My plan is to compute ...
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29 views

Question about piecewise exponential distribution

This is an excerpt from the following paper. I am particularly interested in knowing how the authors got the displayed equations. We let [Z] denote the distribution of a generic random variable ...
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152 views

Determine where hazards starts to increase for a continuous variable

I'm interested in a continuous variable, namely blood pressure. The higher the blood pressure, the greater the risk of heart attack and stroke. However, studies frequently report that also low blood ...
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57 views

What is a hazard rate?

What is the definition of a hazard rate? What is a hazard function? I thought it was the probability that a unit does not survive the time period conditional on being alive, but I see hazard rates ...