Displaying 20 results from an estimated 8000 matches similar to: "Prediction in Cox Proportional-Hazard Regression"
2012 Jul 06
1
How to compute hazard function using coxph.object
My question is, how to compute hazard function(H(t)) after building the
coxph model. I even aware of the terminology that differs from hazard
function(H(t)) and the hazard rate(h(t)). Here onward I wish to calculate
both.
Here what I have done in two different methods;
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2012 May 02
1
coxph reference hazard rate
Hi,
In the following results I interpret exp(coef) as the factor that multiplies
the base hazard rate if the corresponding variable is TRUE. For example,
when the bucket is ks008 and fidelity <= 3, then the rate, compared to the
base rate h_0(t), is h(t) = 0.200 h_0(t). My question is then, to what case
does the base hazard rate correspond to? I would expect the reference to be
the first
2012 Jul 12
1
Cox proportional hazard model and coefficients
Hi,
Here is the summary-output of the Coxph-model I used (the output is based on
the best final model i.e. all significant explanatory variables and their
interactions are included):
coxph(formula = Y ~ LT + Food + Temp2 + LT:Food + LT:Temp2 +
Food:Temp2 + LT:Food:Temp2)
n= 555
coef exp(coef)
se(coef) z
2006 Apr 03
2
testing proportional hazard in a Cox model including a time-varying covariate
I am using a syntax like coxph(Surv(start, stop, event) ~ X, data) to estimate the effect of X, which may change at each measurement (every 6 months). Is there anyone who knows a way to test the proportional hazard assumption in that case?
Thank you in advance
Jean-François Boudreau
Sherbrooke University
[[alternative HTML version deleted]]
2011 Nov 20
1
Cox proportional hazards confidence intervals
I am calculating cox propotional hazards models with the coxph
function from the survival package. My data relates to failure of
various types of endovascular interventions. I can successfully
obtain the LR, Wald, and Score test p-values from the coxph.object, as
well as the hazard ratio as follows:
formula.obj = Surv(days, status) ~ type
coxph.model = coxph(formula.obj, df)
fit =
2010 Nov 24
2
Is there an equivalent to predict(..., type="linear") of a Proportional hazard model for a Cox model instead?
Hi all,
Is there an equivalent to predict(...,type="linear") of a Proportional hazard
model for a Cox model instead?
For example, the Figure 13.12 in MASS (p384) is produced by:
(aids.ps <- survreg(Surv(survtime + 0.9, status) ~ state + T.categ +
pspline(age, df=6), data = Aidsp))
zz <- predict(aids.ps, data.frame(state = factor(rep("NSW", 83), levels =
2010 Nov 13
2
interpretation of coefficients in survreg AND obtaining the hazard function for an individual given a set of predictors
Dear R help list,
I am modeling some survival data with coxph and survreg (dist='weibull') using
package survival. I have 2 problems:
1) I do not understand how to interpret the regression coefficients in the
survreg output and it is not clear, for me, from ?survreg.objects how to.
Here is an example of the codes that points out my problem:
- data is stc1
- the factor is dichotomous
2009 May 05
3
Cox Proportional Hazard with missing covariate data
Dear friends,
I have used R for some time now and have a tricky question about the coxph-function: To sum it up, I am not sure whether I can use coxph in conjunction with missing covariate data in a model with time-variant covariates. The point is: I know how "old" every piece that I oberserve is, but do not have fully historical information about the corresponding covariates. Maybe you
2010 Nov 16
1
Re : interpretation of coefficients in survreg AND obtaining the hazard function for an individual given a set of predictors
Thanks for sharing the questions and responses!
Is it possible to appreciate how much the coefficients matter in one
or the other model?
Say, using Biau's example, using coxph, as.factor(grade2 ==
"high")TRUE gives hazard ratio 1.27 (rounded).
As clinician I can grasp this HR as 27% relative increase. I can
relate with other published results.
With survreg the Weibull model gives a
2010 Nov 15
1
interpretation of coefficients in survreg AND obtaining the hazard function
1. The weibull is the only distribution that can be written in both a
proportional hazazrds for and an accelerated failure time form. Survreg
uses the latter.
In an ACF model, we model the time to failure. Positive coefficients
are good (longer time to death).
In a PH model, we model the death rate. Positive coefficients are
bad (higher death rate).
You are not the first to be confused
2005 Jun 10
1
Estimate of baseline hazard in survival
Dear All,
I'm having just a little terminology problem, relating the language used in
the Hosmer and Lemeshow text on Applied Survival Analysis to that of the
help that comes with the survival package.
I am trying to back out the values for the baseline hazard, h_o(t_i), for
each event time or observation time.
Now survfit(fit)$surv gives me the value of the survival function,
S(t_i|X_i,B),
2007 Dec 04
2
weighted Cox proportional hazards regression
I'm getting unexpected results from the coxph function when using
weights from counter-matching. For example, the following code
produces a parameter estimate of -1.59 where I expect 0.63:
d2 = structure(list(x = c(1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,
1, 0, 0, 1, 0, 1, 0, 1, 0, 1), wt = c(5, 42, 40, 4, 43, 4, 42,
4, 44, 5, 38, 4, 39, 4, 4, 37, 40, 4, 44, 5, 45, 5, 44, 5), riskset =
2009 Mar 26
1
Centring variables in Cox Proportional Hazards Model
Dear All,
I am contemplating centering the covariates in my Cox model to reduce
multicollinearity between the predictors and the interaction term and
to render a more meaningful interpretation of the regression
coefficient. Suppose I have two indicator variables, x1 and x2 which
represent age categories (x1 is patients less than 16 while x2 is for
patients older than 65). If I use the following
2010 Mar 09
1
Question on passing in parameter to Cox hazard
Hi,
I wanted to do the cox model using a matrix. The following lines illustrate what I want to do:
--------------------------------
dat <- matrix(rnorm(30), ncol=3,dimnames = list(1:10,letters[1:3]))
Survival <- rexp(10)
Status <- ifelse(runif(10) < .7, 1, 0)
mat <- as.data.frame(cbind(dat,Survival,Status))
cmod <- coxph(Surv(Survival, Status) ~ a+b+c, mat)
2011 Dec 10
2
p-value for hazard ratio in Cox proportional hazards regression?
Hi,
I'm new to R and using it for Cox survival analysis. Thanks to this great forum I learned how to compute the HR with its confidence interval.
My question would be: Is there any way to get the p-value for a hazard ratio in addition to the confidence interval?
Thanks,
Thierry
--
Thierry Panje Visiting Student Researcher
Department of Psychology Stanford
2012 Feb 20
1
Reporting Kaplan-Meier / Cox-Proportional Hazard Standard Error, km.coxph.plot, survfit.object
What is the best way to report the standard error when publishing
Kaplan-Meier plots? In my field (Vascular Surgery), practitioners
loosely refer to the "10% error" cutoff as the point at which to stop
drawing the KM curve. I am interpreting this as the *standard error
of the cumulative hazard*, although I'm having a difficult time
finding some guidelines about this (perhaps I am
2006 Jul 11
2
Proportional Hazard Function and Competing risks
How can I model coxph() in combination with competing risks
i.e. I have two events and for event the object will leave the data set.
So :
Coxph(Surv(time,event)~....) the event is for all my objects 1.
How can I model this?
Sharon
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2008 Aug 06
1
Variance-covariance matrix for parameter estimates
Dear All,
I am currently working with the coxph function within the package survival.
I have the model h_ij = h_0(t) exp(b1x1 + b2x2) where the indicator
variables
are as follows:
x1 x2
VPS 0 0
LTG 1 0
TPM 0 1
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2004 Sep 22
1
Cox proportional hazards model
Good afternoon,
I am currently trying to do some work on survival analysis.
- I hope to seek your advice re: 2 questions (1 general and 1 specific)
(1) I'm trying to do a stratified Cox analysis and subsequently
plot(survfit(object)). It seems to work for some strata, but not for
others.
I have tumor grade, which is a range of 1 - 4.
When I divide this range of 1:4 into 2 groups, it
2007 May 17
1
Stratified Cox proportional Hazard Model
Hello everyone,
I am a new user of R. Does anybody know how hazard ratios are extracted
for each factor level in a stratified Cox proportional hazard
regression model? I have a cancer data set where the variable
?differentiation? is a factor with three levels: poor, intermediate and
good. I would like to extract the hazard ratio for each grade level and
relate it to another prognostic factor.