All Questions
Tagged with cox-model regression
213 questions
2
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1
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353
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Cox regression assessing joint relationship between baseline groups? JAMA example
I'm a new R user trying to better understand the analytical framework behind an important JAMA paper (doi:10.1001/jama.291.2.210) and how it can be coded in R. It's objective was to evaluate if, in ...
- 79
3
votes
1
answer
1k
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Categorising a continuous variable for Cox proportional hazards analysis using "quartiles by event"
A colleague just told me that he categorises continuous data in survival analysis using "quartiles by event". He essentially uses cut-off points that equally distribute events into four ...
- 55
2
votes
1
answer
304
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Cox proportional hazards with left-censored time-dependent covariates
I'm doing statistical analysis on a cancer study. My specific dataset contains id, various co-variates such as age, sex, metastatic burden, etc. and time to event data for overall survival
I want to ...
- 55
1
vote
1
answer
287
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Can I estimate the COX regression using OLS
I am wondering if I can estimate the Cox regression $h(t,z)= h_0(t)exp(\beta_1 z_1+\dots+\beta_x z_x)$ model using OLS. The idea would be to rewrite the model with regards to the structure of a simple ...
- 61
0
votes
2
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542
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Deriving survival from hazard function
EDIT: It was a simple typo (+ instead of *), but the values still aren't quite right. Leaving the original in case others find it useful
I'm fairly new to working with survival functions so this ...
- 105
1
vote
2
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422
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Survival Analysis for predicting next car's maintenance
I am working on a predictive maintenance project. To simplify I want to predict for a car the next time it will have to change for example the oil filter (and then extend to other parts like wipers).
...
- 11
0
votes
2
answers
680
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Calculating hazard using Cox regression
I'm using the Cox regression model in lifelines (python) to try and predict what the probability of a patient surviving X days is given several variables.
Do to some very silly restrictions on the ...
- 105
1
vote
1
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31
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Should I use cox regression for this?
Should I be using cox regression for this?
I am analyzing the performance of a tennis player. I want to understand how long on average his performance starts to drop during a match.
I indicate an ...
- 11
0
votes
0
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191
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weird outlier in a cox regression model
I'm using normal deviate residual to identify outliers, and I'm confused that my plot seems to suggest that there are unreasonably a lot of outliers...? Has anyone seen something like this?
...
- 381
3
votes
2
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186
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Should I use Cox model?
In a study of crowdfunding, I am investigating the relationship between the reputation of a person seeking funding for a project (a continuous variable) and the proportion of funding target received (...
- 715
1
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1
answer
80
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Explanatory variables that are monotonic functions of time in Cox proportional hazards models?
I am fitting a Cox PH model where the main explanatory variable is a monotonic function of time. Is this violating any assumptions of the Cox model?
- 23
2
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1
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2k
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Cox PH - R 'rms' package - Concordance (Train, CV & Test)
Please could someone verify if my methodology for calculating these three versions of concordance are correct when using the rms package? I have really struggled to ...
- 479
2
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0
answers
110
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Check if PH or AFT model should be fit
It is unclear to me when it is appropriate to fit an accelerated failure time (AFT) model rather than a proportional hazard (PH) model.
I've tried googling and it appears as though PH models are ...
- 635
5
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0
answers
4k
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How to better understand when to use Weibull AFT versus Cox Model for Failure Data
I am struggling to understand when I should consider using a Cox regression model versus using a Weibull AFT model to predict the end of life of mechanical components.
I have tried to apply the Cox ...
- 95
1
vote
1
answer
575
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What does the output of a Cox Proportional Hazard model mean?
For a linear regression plugging different X values to the fitted model gives us the different predicted Y values, for a logistic regression we get the different log odds: what does the output of the ...
- 279
0
votes
1
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775
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Transformations in a Cox Model
I am standardizing all my continuous covariates (and log transforming them to minimize undue influence). However I would like to express the change in the log hazard per 10 year change for my ...
- 367
1
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0
answers
47
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How can I determine whether my Cox regression analysis have enough power to conclude an outcome
I have 159 tumor patients, of which I know several parameters: age, sex, stage, ... and x.
X is a continuous covariate corresponding to the percentage of tumor cells currently dividing (biological ...
- 259
2
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0
answers
83
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Results of a survival analysis change when converting the data to counting process format
Consider the following simple example:
...
- 3,433
1
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1
answer
771
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Interaction not significant in Cox regression model?
I ran a cox model with an interaction between two categorical variables (sex and treatment group) included like:
...
- 381
1
vote
1
answer
1k
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Baseline hazard function is the hazard function obtained when all covariates are set to zero
I am trying to learn Cox proportional hazard model but I have hit a wall with the basehaz function.
Lets suppose for example I have some data that I want to use ...
- 33
2
votes
2
answers
5k
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How to choose the best combination of covariates in Cox multiple regression?
I am performing a multivariate Cox regression analysis, and would like to find what combination of those covariates best predict my outcome.
Say I have a list of candidate genes whose expressions ...
- 21
0
votes
2
answers
915
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Cox regression different results with different combinations of variables
I need help understanding how to use cox hazzard model to calculate risk of death in data from a cohort study.
I have a set of data on physical activity and I want to do a cox regression on ...
0
votes
0
answers
45
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Estimating death based on repeating sequence?
Currently I'm working on a project, and I reading up on Survival Regression with Cox’s proportional hazard model, which looks like it will work to answer the questions I want to ask.
My issue is ...
- 101
1
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0
answers
164
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Survival analysis: how to account for immortal time with time-dependent exposure
I am working on a survival analysis to look at time to preterm birth (birth before 37 weeks). I have a time-dependent exposure that can occur anytime at or after 28 weeks, defined using a heaviside ...
- 75
2
votes
2
answers
3k
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Continuous vs Categorical covariate of interest in Cox Regression
I will use aliases throughout to explain my results in brief and a few questions that have propped up in the process.
Suppose I'm interested in the association of baseline measurement of blood ...
- 367
0
votes
2
answers
2k
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SPSS cox proportional hazard model adjusting for age
I'm using SPSS to run cox proportional hazard model. I've five different groups and I need unadjusted and adjusted (for age) HR for all of them separately. My first group is a reference group. I've ...
- 15
0
votes
1
answer
731
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When doing Cox regression, what should we take as event duration for censored data, and how should we divide the data into training and testing sets?
I am starting out with survival analysis, and am confused about some things specifically in Cox regression. I have not found a tutorial that explains these things clearly, that's why I'm posting this ...
- 261
5
votes
1
answer
842
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Piecewise survival analysis?
I am trying to analyze time-to-event data (time to completion of a task). Looking at the KM curves, there is a distinct behavioral change around 12 months. This makes sense, because at 12 months there ...
- 356
1
vote
1
answer
2k
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Different length in variable and residuals from the model
After having posted another question on the subject, I'm trying this time on my real data (unfortunately not openly publishable) to find the the best variable transformation that yields linearity in ...
- 593
4
votes
1
answer
449
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Why does regression model theory not use measure-theoretic sigma-field type notation but counting process models do?
I have been studying counting process theory for time to recurrent event processes and am interested in the explicit use of the conditioning set in the model notation;
$$E[dN(t)|\mathcal{F}_{t^{-}}]=\...
- 728
1
vote
1
answer
106
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Cox Regression and Linkage Disequilibrium
I'm trying to figure out the best way to account for linkage disequilibrium in a cox regression, and would really appreciate your advice. I'm testing the effect of a particular allele on overall ...
- 41
3
votes
2
answers
3k
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Why and how does adding an interaction term affects the confidence interval of a main effect?
I was wondering why, in a regression model including an interaction term, the confidence interval of one of the main effects becomes wider.
Consider this Cox regression, where the variable IR_BMI27 ...
- 305
4
votes
2
answers
5k
views
Intuitive explanation of censored data in a Cox model
I use Cox regression (proportional hazards) to model survival for a cohort of patients. Patients are censored (alive (0), dead (1)).
I was wondering how Cox regression uses censored data intuitively. ...
- 51
0
votes
1
answer
73
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Cox model with a predictor variable within only one stratum
I'm investigating survival in a cancer patients cohort. The Cox model I'm using is stratified by stage and adjusted for several variables. I would like to add one variable RT (Radiotherapy) which is ...
- 5
2
votes
2
answers
547
views
How can I visualize fitting survival data to a proportional hazards model with a continuous variable?
I have (censored) survival data that I am fitting with a proportional hazards model with a continuous covariate, X (for my purposes, X ranges from 0 to 1). After fitting the model, I get a ...
- 121
2
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1
answer
4k
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Cox Proportional and Pooled logistic regression in a observational cohort study - laymans terms
So my brain is just not understanding the difference between the two above.
I am currently writing a literature review and have to explain the significance of what was found in the research.
The ...
- 29
1
vote
0
answers
66
views
Cox Regression Model for toxicity
I'm trying to evaluate the toxicity of a certain treatment over time. I have 2 independent groups and I apply a treatment to one, and nothing to the second one. I thought about using logistic ...
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3
votes
1
answer
4k
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Converting a Continuous variable to categorical for Cox regression
In a Cox regression model where our variable of interest is continuous (e.g., a lab measurement);
If we want to obtain something other than a unit risk ratio for that variable (e.g., the hazard ratio ...
0
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1
answer
2k
views
How to interpret Coxnet in R?
I am using Coxnet package for a dataset of 457 observations and 180 variables and also for another dataset of 457 observations and 25000 variables.
...
0
votes
0
answers
32
views
Can I incorporate differencing into a (Cox) survival model?
I am predicting college student dropout with a Cox model. I believe that a declining grade point average (GPA) is predictive of dropout, and I want to incorporate this into my model. I'm looking for ...
- 2,692
2
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0
answers
214
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independence assumption on events in Cox model
In the wikipedia article on the Cox model, in the development of the partial likelihood, it is mentioned that the different subjects are treated "as if they were statistically independent." Is this in ...
- 576
7
votes
1
answer
11k
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How to interpret concordance index in Cox models?
I'm new using the survival package in R. Consider an example provided with the package:
...
- 637
4
votes
1
answer
2k
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Cox survival data with time-varying continuous variable and time fixed covariate
I am interested in the paper entitled "Generating survival times to simulate Cox proportional hazards models with time-varying covariates " (Stat Med. 2012 Dec 20;31(29):3946-58.),and want to simulate ...
- 183
4
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1
answer
39
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Extracting relative risk from survival parameters
Brief background: statins are drugs that lower cholesterol. Trials comparing statins with placebo show that statins lower mortality (in terms of hazard ratio) by almost 20% (hazard ratio 0.8). There ...
- 2,403
2
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1
answer
201
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imputation with penalized (Cox) regression
I'm doing penalized (elastic net) Cox regression. But I also have missing data.
Now, as I understand it, the reason we do multiple imputation is that once we do single imputation, our data points are ...
- 753
2
votes
1
answer
1k
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What if linearity doesn't hold in a cox model?
I have built a multivariable cox model with coxph(). However, I am unable to run ggcoxfunctional() on some of the variables because of missing data.
...
- 165
3
votes
1
answer
691
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Cox Proportional-Hazards Regression vs. Regression modeling of competing risk using Fine and Gray
30000 patients all have one diagnosis in common, 3000 of them have been exposed to a potential risk factor before the common diagnosis. 1500 patients develop a malignancy after the common diagnosis.
...
- 31
2
votes
1
answer
1k
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How does Cox regression estimate time to an event?
In R and Python, Cox regression is specified with duration and event as the dependent variables. However, Cox regression is said ...
- 1,400
1
vote
0
answers
854
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What could be the reasons for why re-scaling variables used in regression helps model performance?
There's already an excellent post on standardizing values used for regression here. In this post, I am using Cox Regression (Cox Proportional Hazard model) with the lifelines Python library. Now, one ...
- 1,400
3
votes
0
answers
65
views
Approach to a complex survival analysis
Hello and thanks for reading!
I'm a student who has unfortunately 'designed' quite a complicated experiment which I'm struggling to analyse statistically. I do like statistics but my experience is ...
- 31