r Replace only some table values with values from alternate table

Question

This is not a \"vlookup-and-fill-down\" question.

My source data is excellent at delivering all the data I need, just not in in a usable form. Recent changes in volume

Answer 1

In data.table world, this is an "update-join". Join on "Item" and then update the values in the original set with the values from the new set:

library(data.table)
setDT(inv)
setDT(svc)

inv[svc, on="Item", c("onPO","onHand") := .(i.Backordered, `i.Rcv'd`)]

#inv   original table
#svc   update table
#on=   match on specified variable
# :=   overwrite  onPO    with  Backordered
#                 onHand  with  Rcv'd


#          Item onHand demand onPO
# 1:   10100200    600   3300 2700
# 2:   10100201      0     NA   20
# 3:   10100202     39     40    1
# 4:   10100203      0     40   40
# 5:   10100204      0     NA  100
# 6: 10100205-A     44     NA   18
# 7:   10100206     40     70   30
# 8:   10100207      0    126  126
# 9:   10100208      0     10   10
#10:   10100209      0     10   10
#11:   10100210      0    250  250