You should only need this part
dt << Recode Column(
AsColumn(dt, 4),
{Map Value(_rcOrig, {., 0}, Unmatched(_rcNow))},
Update Properties(1),
Target Column(AsColumn(dt, 4))
);
where you define your column index inside AsColumn.
If I have table like this
and I wish replace missing values of column index 1 and 3, I would use
dt << Recode Column(
As Column(dt, 1),
{Map Value(_rcOrig, {., 0}, Unmatched(_rcNow))},
Update Properties(1),
Target Column(As Column(dt, 1))
);
and
dt << Recode Column(
As Column(dt, 3),
{Map Value(_rcOrig, {., 0}, Unmatched(_rcNow))},
Update Properties(1),
Target Column(As Column(dt, 3))
);
(number inside As Column has changed)
-Jarmo