[R] ordering of additional columns in forest plot in meta package

[Philip de Witt Hamer]

Hi,

I am trying to add additional columns to a forest plot using the meta package.
The study information and subgroup analysis plotting is handled properly.
For this output the data is ordered first by subgroup label
(rnd.subgroup1 in the example) and second decreasing size of totals
('n' in the example).
The proper ordering of this data is confirmed by the color coding
(black and red in the example) of the subgroup label. Also the
"studlab","event" and "n" are all ordered correctly.

The probIem now is that I cannot get the added columns
("rnd.subgroup1" and "rnd.subgroup2") to follow this same proper
ordering.

library(meta)
# dummy data
nr.studies <- 20
rnd.subgroup1  <- round(rnorm(nr.studies,1.5,.1),0) # random 1s and 2s
rnd.subgroup2  <- c(letters[1:nr.studies]) # ordered unique letters
lbls       <- c(letters[1:nr.studies]) # letters as surrogate study
labels 'author et al, year'
event      <- round(rnorm(nr.studies,10,5),0) # random event nrs
event[event<0]<-0 # to avoid a negative value error
n          <- round(rnorm(nr.studies,100,25),0) # random totals
mydata     <- data.frame(cbind(lbls,rnd.subgroup1,rnd.subgroup2,rnd.subgroup3,event,n))
mydata
a     <- metaprop(event,n,studlab=lbls)
a$rnd.subgroup1 <- addvar(a,mydata,"rnd.subgroup1",by.y="lbls")
a$rnd.subgroup2 <- addvar(a,mydata,"rnd.subgroup2",by.y="lbls")
grid.newpage()
forest(a,
	studlab=lbls,
	comb.fixed=T,comb.random=F,overall=T,
	text.fixed="my title here",
	byvar=rnd.subgroup1,
	print.byvar=T,
	leftcols=c("studlab","rnd.subgroup1","rnd.subgroup2","event","n"), #
sort order not right for 'rnd.subgroup1' and 'rnd.subgroup2'
	bylab=c("one","two"),
	sortvar=-n,
	col.i=rnd.subgroup1,
	col.by=c("royalblue"),
	xlim=c(0,.5)
)

I suspect that it may have to do with an omitted indexing command in
the forest function.
Your input in kindly appreciated.

Philip de Witt Hamer, MD PhD

VU medical center
dept neurosurgery
PO Box 7057
1007 MB Amsterdam
The Netherlands