In survival analysis, the hazard rate at time $t$ is the instantaneous probability of death at $t$, conditional on survival until $t$.

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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 ...
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8 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 ...
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21 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 ...
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11 views

Using Hazard Ratio to predict Population Incidence or Prevalence

The univariate hazard ratio corresponding to a per unit continuous linear increase between a risk score and a disease is 1.04 (literature) . I am interested in using this hazard ratio to predict the ...
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1answer
49 views

Calculating constant hazards in exponential survival distributions in R using survreg()

In an ecological seed removal experiment, we have seed removal data from 720 seed plates with 25 seeds each. For each plate, we know the number of "surviving" seeds at several times ti until the end ...
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1answer
123 views

Simulate a random variable having piecewise gamma failure rate

I am having trouble in simulating values for a random variable $X$ having a piecewise gamma failure rate: $$ \lambda_X(t) =\lambda_1(t)1\!\!1_{\lbrace t\leq t_0 \rbrace} + \lambda_2(t)1\!\!1_{\lbrace ...
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1answer
30 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 ...
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1answer
65 views

Survival Analysis Applied when Individuals that “Died” can still Return

I'm running an AB Test and using Survival Analysis to estimate the Return Rate to the website. Each day (in a total of 7 days) I randomly assign 100 users to group A and 100 users to group B and ...
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2answers
71 views

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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1answer
64 views

Intuitive meaning of the limit of the hazard rate of a gamma distribution

For a Gamma distribution with shape parameter $\alpha >1$ and scale parameter $\beta > 1$, one can show that its hazard rate function $h$ is increasing and satisfies \begin{equation} ...
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43 views

Tail problem with hazard function

Before doing a more advanced survival analysis, I generated an exponentially distributed variable in Stata and used the following code to get a constant hazard rate graph: "sts graph, hazard" I get ...
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1answer
99 views

Comparing failure rates between 2 products with different number of deployed equipment

I have the following scenario, which I am trying to better understand. There are 2 different brands or groups of devices performing the same functionality as such: - Product/Brand 1 has 4,323 devices ...
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1answer
142 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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24 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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47 views

How to demonstrate biased estimates of linear regression vs cox proportional hazard survival analysis in R?

I want to perform a really simple simulation of right censored data. Then I want to draw a kaplan meir survival curve and do a cox proportional hazards test. Then I also want to perform a simple ...
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2answers
81 views

Hazard function, survival function, and retention rate

What is the difference between the hazard function, survival function, and retention rate in survival analysis?
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19 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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34 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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1answer
46 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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1answer
46 views

What do these probabilities mean in lay language? A HR of 0.419 means what?

The adjusted hazard ratios (HRs) for dementia were significantly inversely associated with increased daily or total equivalent statin dosage. The HRs for the three tertiles of mean equivalent daily ...
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Ordered Hazard Model in a 2-stage selection regression?

I'm writing with what is probably a pretty dumb question. But Google searches aren't revealing what I'm looking for, so I thought I'd come to the experts! Context I am interested in looking at ...
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32 views

Cause-specific hazard in R

library(cmprsk) library(muhaz) set.seed(2) time <- rexp(100,2) cause <- sample(0:1,100,replace=TRUE) mod = muhaz(time,cause) plot(mod) The above R code ...
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38 views

Discrete survivor function expressed in terms of hazard

Let $T$ can take on values $t_1,t_2,\ldots,$ with $0\le t_1\le t_2,\ldots,$ and let the probability function be $$f(t_j)=Pr(T=t_j),\quad j=1,2,\ldots$$ The survivor function is then $$S(t)=Pr(T\ge ...
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1answer
98 views

Fractional polynomials in PHREG procedure

For regression analysis by fractional polynomials i used the PHREG procedure in SAS. But it didn't give any Hazard Ratio values. Is it normal or any mistake in my code? ...
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51 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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69 views

Which model to use for survival analysis when there are different times of entry into the sample?

I have a data set containing the trades executed by many traders as follows: ...
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122 views

Differences between logistic regression parameter estimates and Cox-proportional hazard parameters

We have been working on a survival analysis. We are examining tree seedling survival over a decade with annual to biannual census intervals. We have been using the package coxme in R for a mixed ...
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29 views

Bivariate gamma distribution with one parameter marginal

Suppose two random variables X,Y>0, have a joint gamma distribution. Its marginal for X is G(a,b) and that for Y is G(a,c). For identification purposes, normalization is needed.does anyone know if ...
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29 views

Hazard ratio can be computed from shrinkage estimators?

I am using LASSO in survival analysis. I wonder if it is valid to compute a hazard ratio (HR) from a lasso coefficient, that is, $\text{HR} = \exp(\text{lasso coef})$? Thank you for any help!
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1answer
134 views

Average hazard rate with Cox proportional hazard model always larger than the hazard rate without any explanatory variables?

I am estimating a Cox proportional hazard model with and without explanatory variables. Without explanatory variables, the hazard rate is just the proportion of all individuals that failed at time ...
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88 views

How to calculate Hazard Ratio from Kaplan Meier curve

Is it possible to calculate the Hazard Ratio, Log[HR], and SE for overall survival (OS) using data from a manuscript that presents Kaplan Meier curve for OS? Usually these manuscripts present the ...
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38 views

Implication of Hazard Rate?

So from my understanding, the hazard rate is not a probability but a rate of an event happening at any one period of time. Can someone please tell me the implications of a hazard rate value. Would ...
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37 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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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
131 views

How to conduct Cox PH stratisified by matched pair in R

I am wanting to calculate hazard ratio in a matched cohort design. For such I am using the coxph() function in R. But I have been recommended to stratify by matched ...
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1answer
431 views

Find the mode of a probability distribution function

I am trying the find mode of a probability distribution function given by \begin{equation} g(x/\alpha,\beta,\sigma)=\frac{1}{\Gamma \left( \alpha ...
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1answer
178 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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1answer
43 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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1answer
225 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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1answer
60 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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2answers
683 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 ...
2
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32 views

Hazard ratios for three groups - does deleting one group affect the remaining ratio?

My study originally had 3 groups, x , y and z. Hazard ratios were reported for x vs y, x vs z and y vs z. If we remove group z from the study, would the x vs y hazard ratio change? If someone can ...
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1answer
90 views

Survival analysis where P(event) < 1

Suppose you are interested in analyzing time to event data for a sample of patients. You are interested in the time elapsed until a patient contracts an illness. However, a majority of patients will ...
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1answer
153 views

different HRs and corresponding CIs with cph and coxph

I tried a model using cph and coxph: ...
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22 views

Is it possible to add 2 ore more Hazard factors?

I'm a general practicioner and I'm trying to estabilish a conection between interarm sistolic blood pressure difference with cardiovascular disease but i dont have time to wait 10 years or more to ...
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1answer
33 views

Compute the cumulative hazard of a time interval

I'm a little confused in calculating the cumulative hazard within a time interval. We know that $H(t)=\int^{t}_{0}h(u)du$, if I have $\Delta t=t_1-t_0$ (1) $H(\Delta t)=\int^{\Delta t}_{0}h(u)du$ ...
0
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1answer
264 views

Is it possible to construct a discrete-time multilevel hazard model in R?

I'm trying to run a discrete-time multilevel hazard analysis comparable to the model proposed by Barber et al. I am attempting to model the hazard of migrating internationally using predictors at the ...
4
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1answer
100 views

It it possible in R to specify a regression formula for the hazard rate for a survival analysis model?

I am currently trying to fit a survival analysis model which has the following survival function: $S(t) = \lambda_i e^{-\lambda_i t}$ but with $\lambda_i = e^{\beta_0 +\beta_1 log(1+X_i)}$ where ...
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1answer
40 views

Calculate Hazard Ratio Manually for Continous Covariate

I found an example for manually calculating the hazard ratio when there are two groups. ...
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52 views

Outliers in proportional hazards model

How can one easily found an outlier in PH model and why are they so important? Can anybody give me some advice or suggest which R function may I use? Thanks for comments and help.