Hello,

I'm trying to create birth centile charts from about 90000 birth weights using the package lmsqreg. As this is not a CRAN package I have problems finding any examples, which explain how to estimate the LMS parameters needed for the equivalent degrees of freedom. (I only have some basic understanding of statistics, I roughly understand the formulas, but then I don't know how to recreate them in R.) Does anyone have an example?

So far I have done this:

library(lmsqreg)
centiles <- c(0.004,0.02,0.09,0.25,0.5,0.75,0.91,0.98,0.996)
lms.fit <- lmsqreg.fit(boys.o$BIRTH_WEIGHT,boys.0$GEST_AGE,edf=c(3,5,3),pvec=centiles)
plot(lms.fit)
points(boys.0$GEST_AGE,boys.0$BIRTH_WEIGHT)

I also plotted the median and the coefficient of variation by gestation age, but then I'm struggling to find the correct command to plot the Box-Cox power by gestation age. (Does it makes sense to compute all centiles in one go?)

Thanks  Joanne

P.S.: I found a couple of recent articles that refer to the GAMLSS package, but that looks even more complicated to me.



###################
Running R on Windows XP

> sessionInfo()
R version 2.10.1 (2009-12-14) 
i386-pc-mingw32 

locale:
[1] LC_COLLATE=English_United Kingdom.1252 
[2] LC_CTYPE=English_United Kingdom.1252   
[3] LC_MONETARY=English_United Kingdom.1252
[4] LC_NUMERIC=C                           
[5] LC_TIME=English_United Kingdom.1252    

attached base packages:
[1] stats4    splines   stats     graphics  grDevices utils     datasets 
[8] methods   base     

other attached packages:
[1] VGAM_0.7-10   lmsqreg_0.0-6 MASS_7.3-5    quantreg_4.44 SparseM_0.83 

loaded via a namespace (and not attached):
[1] tools_2.10.1
 

> Sys.getlocale()
[1] "LC_COLLATE=English_United Kingdom.1252;LC_CTYPE=English_United Kingdom.1252;LC_MONETARY=English_United Kingdom.1252;LC_NUMERIC=C;LC_TIME=English_United Kingdom.1252"
> 

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