R help - Dec 2008 - Left-truncated regression

Hi.

I am looking for a function for left-truncated data.
I have one data set with 2 variables (Hours~Yrs_Ed).
I already left-censored the data at 200 and left-truncated it at the same
spot, so that I am able to make 2 estimations (one for censoring and one for
truncation).
I know how to make the linear regression for the left-censored variable
(hours) and how to plot the regression line into the (x,y) plot (packages
AER, Zeileis, Survival, ...):

tfit<-survreg(Surv(Hours,Hours>0,
type='left')~Yrs_Ed,data=DataWomen,dist='gaussian')
z<-predict(tfit,type="response")
plot(Yrs_Ed,Hours)
abline(tfit)

My aim is to compare the effects of truncation and censoring graphically by
plotting the two regression lines into one plot with both datasets (censored
and truncated).
I just can't figure out how to write the function for left-truncated data
and what package to use for this. I only need "left-truncation", not
"left-truncation and right-censoring".
I hope somebody can help me with that matter.

Zita


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Look at the sand package, which is available at

   http://www.csm.ornl.gov/esh/statoed/

and the NADA package, which is available from CRAN. One or both may have
items of interest.

Tom



Zita wrote:
> 
> Hi.
> 
> I am looking for a function for left-truncated data.
> I have one data set with 2 variables (Hours~Yrs_Ed).
> I already left-censored the data at 200 and left-truncated it at the same
> spot, so that I am able to make 2 estimations (one for censoring and one
> for truncation).
> I know how to make the linear regression for the left-censored variable
> (hours) and how to plot the regression line into the (x,y) plot (packages
> AER, Zeileis, Survival, ...):
> 
> tfit<-survreg(Surv(Hours,Hours>0,
> type='left')~Yrs_Ed,data=DataWomen,dist='gaussian')
> z<-predict(tfit,type="response")
> plot(Yrs_Ed,Hours)
> abline(tfit)
> 
> My aim is to compare the effects of truncation and censoring graphically
> by plotting the two regression lines into one plot with both datasets
> (censored and truncated).
> I just can't figure out how to write the function for left-truncated
data
> and what package to use for this. I only need "left-truncation",
not
> "left-truncation and right-censoring".
> I hope somebody can help me with that matter.
> 
> Zita
> 
> 
> 
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http://www.nabble.com/Left-truncated-regression-tp20789446p20798448.html
Sent from the R help mailing list archive at Nabble.com.