[BioC] Differentially expressed gene list

[carotenuto@igb.cnr.it]

Hi,when I perform SAM on  my array data(siggenes)I have some problems in 
retrieving the separate lists of up regulated and down regulated genes.
When I write:
fold<-function(x){				
gruppi<-split(x,controllo)
geni1<-abs(mean(gruppi[[2]])-mean(gruppi[[1]]))
return(geni1)
}
fold<-esApply(expr.contr.tratt.4,1,fold)
filtro.geni.4_prova<-expr.contr.tratt.4[which(fold>=1),]
filtro.geni.4_prova

everything is working well and I can obtain the correct HTML output,but if I 
write the same using fold change<1 to obtain downregulated genes,I have the 
following  warning message:

###Warning messages:
####1: the condition has length > 1 and only the first element will be used in: 
if (!nchar(text <- getText(object))) return("") 
####2: the condition has length > 1 and only the first element will be used in: 
if (!nchar(text <- getText(object))) return("") 
####3: the condition has length > 1 and only the first element will be used in: 
if (!nchar(text <- getText(object))) return("") 
####4: the condition has length > 1 and only the first element will be used in: 
if (!nchar(text <- getText(object))) return("") 
####5: the condition has length > 1 and only the first element will be used in: 
if (!nchar(text <- getText(object))) return("")

Where is the mistake?
Thank you for your help
Sara