Hi there, 

I am trying to use the getSYMBOL function for my IDs, but seem to be stuck:

features = hthgu133pluspmprobe
ID = unique(features[,4])
ID2<-sub("_at","",ID)
ID2<-sub("_AT","",ID2)
GS <- as.matrix(getSYMBOL(ID2, 'org.Hs.eg'))

I get a list of the original IDs and NA values.

What am I doing wrong? Can someone please show me an example for a working script? 

The above conversion is based on the Cibersort CEL -> mixture script by the way.

I appreciate any help. Thanks!

You are doing two things wrong. First, you shouldn't be changing the IDs. I have no idea what the Cibersort CEL -> mixture script might be, but if that's what it says to do, then it's wrong. Second, you are using old tech. Things like getSYMBOL() are outdated, and only work because we value backwards compatibility. You should instead be using either select() or mapIds() on the unadulterated probeset IDs. See ?select or ?mapIds after loading AnnotationDbi for more information.