On the basis of the vectors Label and ID create a character vector newLabel containing labels constructed as ID_xxx_Label, with xxx the value of ID for that field and Label the value of Label for that field.
> head(Label, n = 10)
[1] "Middle" "High" "Low" "High" "Middle" "High" "Middle" "Middle" "High" "Low"
...
> head(ID, n = 10)
[1] 54 115 109 346 298 139 221 447 27 331
...