People, I have found out how to create basic R hash tables and use "ls" and "get" and I can import my JSON hash table file with: x <- fromJSON( file="t.json" ) but if I have previously created x with: x = new.env(hash=T) - as soon as I import from the file, x stops being a hash table . . My file is of the form: [["01.01.01.00",-2.304247814744562], ["01.01.01.01",-2.2880972424951476], ["01.01.01.02",-2.30334683466354], ["01.01.01.03",-2.354963873024918], . . (I have added line feeds for clarity). I want to be able to find the means of the values for the keys of: "x.x.x.00" "x.x.x.01" "x.x.x.02" . . "x.x.x.21" Help appreciated . . Thanks, Phil.