# Questions tagged [accelerated-failure-time]

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### How to predict survival curves with step changes over time

I'm trying to predict the survival curves for customers, knowing that for some rare customers after a certain time the survival probability has a jump. Those jumps are due to endings of minimum ...
• 127
45 views

### What is the model for dist="logistic" in R survreg, and in what unit are the coefficients?

Does anyone know the model and parameterization for surveg with dist="logistic"? I'm having trouble finding documentation anywhere. I checked Chapter 2.2 of Kalbfleisch and Prentice and only ...
41 views

### Xgboost AFT model predicts infinity

I used Xgboost AFT model to predict survival time but get some infinity predictions. Is it normal? How should I interpret that? I changed aft_loss_distribution from 'normal' to 'logistic', then had ...
1 vote
180 views

### Simulate a Weibull regression model

I am trying to simulate a AFT Weibull model in R using a log-linear model \begin{align} log(Y)=\beta_0 +\beta_1 X1+\beta_2 X2+c W \end{align} where $W ~$ a extreme value distribution. below is my ...
• 329
87 views

### Know how to choose appropriate distribution for AFT

It is written in many web resources that the distribution of the accelerated failure time model must be specified correctly but I don't think I've seen anything about how to know this. I see often ...
• 345
83 views

### Relationship between Survival Distributions and Log Linear Regression in Accelerated Failure Time models

The accelerated failure time model (AFT) can be expressed as: $S_{1}(t) = S_{0}(\frac{t}{\gamma})$ where $S_{0}$ is a specified baseline survival distribution and $\frac{1}{\gamma}$ is the accelerant/...
• 33
1 vote
134 views

### How to formulate and simulate data from an accelerated failure time model?

I understand that an accelerated failure time model can be conceptualized as a cox model which includes covariates whose effects depend on actual time, so the convenient expression of the partial ...
• 57.2k
280 views

### What is the meaning of the flexsurvreg plot and its res.t?

I use the flexsurverg to estimate the a Weibull survival model with a time varied covariate, where “utility” is a continuous function, and the result is shown as follows: I plot the fit function and ...
1 vote
628 views

### AFT model interpretation

I am slightly confused about the way accelerated failure time models work in comparison to proportional hazard models. Is it a correct statement that while the PH model assumes covariates multiply ...
• 325
1 vote
149 views

### Weibull and Lognormal Fits

I have simulated failure time data for some components. I tested whether a Weibull or lognormal distribution best fit the data. Please see Figures below. The figures provide median and $95\%$ ...
• 823
1 vote
139 views

### Recurrent event data modelling - Cox PH or AFT?

I am attempting to model recurrent event data in Stata. My data is dataset of patient records and I am modelling a patients first delivery of a mobility aid and the subsequent deliveries of new ...
• 11
235 views

### flexsurvreg log logistic intercept in R

I'm trying to fit a log-logistic AFT model with flexsurvreg(). With AFT model, $$\log T = \gamma_0 + \gamma_1 z_1 + \gamma_2 z_2 + \sigma W,$$ where W ~ standard logistic distribution. Below is an ... 1 vote
543 views

### Finding a distribution of Accelerated Failure Model

Can someone please answer these 3 questions related to AFT model? In Accelerated Failure Time (AFT) model, $S(t│β,x)=S_0 (exp(β^T x).t)$, where $S_0$ is the baseline survival function, does $S_0$ ...
• 135
271 views

### AFT models in Stata with time-varying covariates

The AFT models from Stata's streg can handle time-varying covaraites. In particular, the manual states that streg is suitable ...
1 vote
21 views

### AFT model with varying production

I want to implement an AFT model to study the failure time of a product given it's width. $$S(t|width)=S_0((\beta_0+\beta_1 \times width)t)$$ However the prodction has varied during the time (less ...
• 113
173 views

### Scale Parameter in a Log-Linear Accelerated Failure Time Model

Let the logarithm of the random varible $T_i$, associated with the lifetime of the $i$th individual in a survival study, follow the disitribution $$log(T_i) = \mu + X_i\beta + \sigma\epsilon_i$$ with \$...
1 vote