[R] regression with paired left-censored data

[David Winsemius]

On Apr 15, 2013, at 8:55 AM, Laura MacCalman wrote:

> 
> HI
> 
> I am trying to analyse data which is left-censored (i.e. has values below the detection limit). I have been using the NADA package of R to derive summary statistics and do some regression. I am now trying to carry out regression on paired data where both my X and Y have left-censored data within them.
> 
> I have tried various commands in R:
> 
> rega = cenreg(Cen(conc, cens_ind) ~ Gp_ident)) 
> with all X and Y data stacked and using a group identifier to look at the differences
> 
> this doesn't take account of the paired data though.
> 
> I have also tried splitting the data and regessing one on the other
> 
> rega = cenreg(Cen(conc1, censind1) ~ Cen(conc2,censind2))
> 
> which doesn't work.
> 
> Does anyone know of a command that will work - or perhaps suggest another package that I could use?
> 
> I have also looked at multiple imputation packages but they all seem to impute data depending on other columns - whereas I would want to impute data between zero and the censored value.
> 
> Any guidance/advice would be very much appreciated.

The `survival::Surv` function allows left censoring and the `coxph` function allows strata or clusters to be specified. My understanding is that for many years analysts used the Cox regression machinery to crank out conditional logistic regression by creating two-member (or 1+n) member strata/cluster. I'm wondering if that could be made to work here, since this seems even closer to a "real" survival analysis problem.

This response from Terry Therneau (looked up with Markmail) to a question about a right-censored situation suggests that the use of cluster() rather than strata() might be be more powerful:

http://markmail.org/message/c2oqqd34nujxvuvi?q=list:org%2Er-project%2Er-help+paired+survival+coxph+strata

-- 
David.


> 
> Laura
> 
> 
>  
> Dr Laura MacCalman Msci MSc PhD Gradstat
> Senior Statistician
> 
> Institute of Occupational Medicine
> Research Avenue North
> Riccarton
> Edinburgh
> EH14 4AP
> 
> Tel: 0131 449 8078
> Fax: 0131 449 8084
> Mob: 07595 054 881
> Email: Laura.MacCalman at iom-world.org
> 
> Web: http://www.iom-world.org
>  
> 
> --------------------------------------------------------------------------
>  
> The Institute of Occupational Medicine (IOM) is a company limited by guarantee, registered in Scotland (No.SC123972) and a Registered Scottish Charity (No.SC000365). IOM Consulting Ltd is a wholly owned subsidiary of IOM and a private limited company registered in Scotland (No. SC205670). Registered Office: Research Avenue North, Riccarton, Edinburgh, EH14 4AP, Tel +44 (0)131 449 8000.
> 
> This email and any files transmitted with it are confide...{{dropped:18}}
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius
Alameda, CA, USA