Re: [R] Interval censored Data in survreg() with zero values!

2009-01-12 Thread Geraldine Henningsen
Hello again, I studied your suggestion but still I disagree. You wrote: "From the way you wrote the problem I assumed that there is some number of n "looks" at the subject and then you count them up." But this is not the case. My data is clearly continuous quantities and no discrete choices

Re: [R] Interval censored Data in survreg() with zero values!

2009-01-06 Thread Geraldine Henningsen
Terry Therneau schrieb: > Apologies -- you are being more subtle than I thought. Nevertheless, I think > that the censoring language isn't quite right. > > You are thinking of a hierarchical model: > > z ~ N(Xb, sigma), where Xb is the linear predictor, whatever covariates > you > thin

Re: [R] Interval censored Data in survreg() with zero values!

2008-12-30 Thread Geraldine Henningsen
> --begin included - > My endogenous variable is not a time depending variable but percentages > which naturally are censored in the interval [0,100]. Unfortunately many > data points are 0 or 100 exactly. The rest of the data is asymmetrically > distributed. So I would like to apply a two-li

Re: [R] Interval censored Data in survreg() with zero values!

2008-12-29 Thread Terry Therneau
--begin included - My endogenous variable is not a time depending variable but percentages which naturally are censored in the interval [0,100]. Unfortunately many data points are 0 or 100 exactly. The rest of the data is asymmetrically distributed. So I would like to apply a two-limit tobit, r

Re: [R] Interval censored Data in survreg() with zero values!

2008-12-26 Thread Geraldine Henningsen
Hello again, thank you very much for your help so far. To be more specific, I generate a simplified data set that is similar to my real world data: set.seed( 123 ) data <- data.frame( x = runif( 200 ), y = NA ) for( i in 1:200 ){ data$y[ i ] <- rweibull( 1, 1, 70 + 10 * data$x[ i ] ) - 30 } d

Re: [R] Interval censored Data in survreg() with zero values!

2008-12-24 Thread Terry Therneau
The problem is that you are not coding your data the way that I would; program authors do not always anticipate what others will do! The Weibull distribution has support on (0, infinity). Using Surv(t1, t2, type='interval2'), you can have a left censored observation where time of even

Re: [R] Interval censored Data in survreg() with zero values!

2008-12-23 Thread Achim Zeileis
On Tue, 23 Dec 2008, Geraldine Henningsen wrote: Hello, I have interval censored data, censored between (0, 100). I used the tobit function in the AER package which in turn backs on survreg. Actually I'm struggling with the distribution. Data is asymmetrically distributed, so first choice would

Re: [R] Interval censored Data in survreg() with zero values!

2008-12-23 Thread Don MacQueen
Surv() allows left, right, or interval censoring. Try left censoring instead of interval censoring. For the weibull or lognormal, think of your data as <=100 instead of [0,100]. -Don At 8:08 PM +0100 12/23/08, Geraldine Henningsen wrote: Hello, I have interval censored data, censored betwee

[R] Interval censored Data in survreg() with zero values!

2008-12-23 Thread Geraldine Henningsen
Hello, I have interval censored data, censored between (0, 100). I used the tobit function in the AER package which in turn backs on survreg. Actually I'm struggling with the distribution. Data is asymmetrically distributed, so first choice would be a Weibull distribution. Unfortunately the Wei