Questions tagged [accelerated-failure-time]
The accelerated-failure-time tag has no usage guidance.
36 questions
0
votes
0
answers
18
views
low AIC on Skew-Normal AFT
I am interested in making an AFT model based on the Skew-Normal distribution. For this I am basing myself on the following article. When running the model and comparing it with others such as Weibull, ...
- 281
1
vote
1
answer
43
views
Cox Proportionall Hazards compared to AFT and the proportional hazards assumption
I am dealing with survival analysis in R in big population datasets with millions of rows. My first option was a cox regression
...
- 33
0
votes
1
answer
28
views
CoxPHFitter and WeibullAFTFitter() lifelines implementation
I am trying to build a survival model to predict years of life lost; currently, I am running several different survival analysis methods to compare their results: AFT and Cox PH.
I am using the ...
- 1
0
votes
0
answers
14
views
Estimating the parameter of Weibull accelerated failure time regression model
The parameters of Weibull AFT regression model are estimated by using the maximum likelihood method for the following model:
Are there different methods of estimation? Please explain them.
- 11
1
vote
1
answer
20
views
The value of scale parameter σ in accelerated failure time model
my model follows Weibull distribution, my question about σ is when we could replace it with one and when we may consider it a scale parameter?
- 11
0
votes
1
answer
26
views
Can I use simple slopes with AFT models?
I am doing a study using accelerated failure time (AFT) log-normal models to predict survival time for a new incarceration (couldn't use Cox PH as the proportional hazards assumption was violated). ...
- 11
0
votes
0
answers
46
views
Constructing nomogram from approximate model in Regression Modelling Strategies
In section 19.5 in Regression Modelling Strategies by Frank Harrell we make an approximate model using linear regression with ols. Since this is an ols object we have to calculate survival quantities ...
- 101
0
votes
0
answers
11
views
Interpreting AFT or Cox PH model in terms of median
An AFT model has been fit, with a binary sex variable. The coefficient estimate of female was 0.416 (reference level is Male). The interpretation of the coefficient is provided as below.:
"This ...
0
votes
0
answers
37
views
What is the distribution of error term in Gompertz AFT model?
Given the AFT model $\ln(T)=\beta+\sigma\times W$, the distribution of $T$ depends on the random term $W$. If $T$ follows a Gompertz distribution with the shape and rate, how can I derive the value of ...
- 57
0
votes
0
answers
50
views
Interpreting AFT Model Coefficients: Mean vs. Median Survival Time in Log-Normal Distribution
When interpreting the coefficients of an Accelerated Failure Time (AFT) model that assumes a log-normal distribution, should we focus on the impact of coefficients on the mean survival time or the ...
- 291
0
votes
0
answers
51
views
Best way to write the likelihood of a model?
Suppose we have the classic AFT (Accelerated Failure Time) model:
$$\log T = -X'\beta + \epsilon$$
I have seen the Likelihood corresponding to this model written in different ways.
For example, I have ...
4
votes
1
answer
132
views
How to write a Gompertz model as an accelerated failure time model?
Accelerated failure time models are usually defined as a model for $X>0$ with (constants) covariates $Z\in \mathbb{R}^p$ such that
\begin{equation}
\log(X) = \mu + \beta^*Z + \sigma W,
\end{...
- 167
1
vote
0
answers
33
views
The AFT and PH model
According to the following - https://dylanspicker.com/courses/STAT437/content/041%20+%20044.%20Lecture%20Notes.pdf
the PH and AFT models are equivalent for Weibull distribution.
Does this implies the ...
- 1,455
2
votes
1
answer
54
views
Counting process equality for linear rank test under AFT model
I am currently reading through the paper:
Estimating Regression Parameters Using Linear Rank Tests for Censored Data - A.A. Tsiatis, Annals of Statistics 18(1): 354-372, 1990.
https://projecteuclid....
- 56
3
votes
1
answer
248
views
R package for Accelerated failure time Models with arbitrary censoring and left truncation
This is a simple exploratory R question i hope somebody can help me with. I am trying to model accelerated failure time models on data that is arbitrarily censored (right, left, or interval censored) ...
- 167
0
votes
1
answer
28
views
How to speed up aftreg estimation?
I am performing an Accelerated Failure Time (AFT) regression data on a panel setting (multiple records per observation with time-dependent variables) using the eha ...
- 179
3
votes
1
answer
671
views
Choice between Proportional Hazard and Accelerated Failure Time survival models
How can I determine whether to use proportional hazard (PH) or accelerate failure time (AFT) survival models in order to analyze my data?
Are there any established guidelines or common practices that ...
- 363
0
votes
0
answers
48
views
Options on modelling a hazard function with a turning point
I have some survival data and need to fit survival models to it and extrapolate. I plotted the log cumulative hazard and empirical hazard plot (using muhaz). There appears to be a change in the hazard ...
- 761
0
votes
1
answer
617
views
How do I choose correct model (AFT or PH) & distribution when Cox proportional hazards is not appropriate?
I have been tasked with evaluating hospital length of stay (LOS) in two groups of patients using the Cox proportional hazards model. One group of patients received a medication, the other did not. ...
- 1
1
vote
1
answer
120
views
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 ...
- 281
0
votes
1
answer
125
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 ...
0
votes
0
answers
172
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
2
votes
1
answer
600
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 ...
- 431
3
votes
1
answer
282
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
2
votes
1
answer
413
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 ...
- 64.8k
0
votes
1
answer
715
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 ...
- 57
2
votes
1
answer
2k
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 ...
- 555
1
vote
0
answers
508
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 $95\%$ ...
- 843
2
votes
1
answer
314
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 ...
- 21
0
votes
1
answer
494
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 ...
nens
1
vote
1
answer
1k
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 $S_0$ ...
- 145
3
votes
1
answer
428
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 ...
- 2,554
1
vote
1
answer
32
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
3
votes
2
answers
468
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 $...
- 543
1
vote
1
answer
533
views
D-Calibration for Survival Models with imbalanced outcomes
I am building an accelerated time failure (AFT) model on a highly imbalanced data set 90% survival 10% death. I understand that we can not use Brier score because of the outcome imbalance, Brier score ...
- 11
1
vote
1
answer
1k
views
Assumptions of an Accelerated Failure Time model?
I have an AFT model, comparing the adjusted survival of 5 groups and seeming to give reasonable results. As I do not feel confident in survival modelling, does this model has assumptions that need to ...
- 2,267