>We are reasonably new users of MAP/INFO and have an interesting challenge.
Leo,
The way to do it is to "split" all the objects in one table using all the
objects in the second table, then use a spatial join to combine the data.
Here is how I would overlay tables A and B (using MI 4.5):
1. Save a copy (C) of one of the tables (A).
2. Open table C and add columns to hold values from B, also add a polygon
ID column.
3. Open a map window with layers B and C.
4. Make layer C editable; select all from C; Objects -> Set Target.
5. Select all from B; Objects -> Split. Select "Value" disaggregation
method for columns with data, "Blank" for the new columns.
6. Update your polygon ID column using the expression "rowid" (no quotes).
7. For each column needed from table B:
Table -> Update Column...
Table to Update: C
Column to update: <whatever>
Get value from table: B
Join... where object from table B contains object from table C
Calculate: Value of: <whatever>
Unfortunately the "Update" mapbasic statement doesn't handle joins (one has
to use the slightly bizarre "add column" instead) so there's no quick way
to update multiple columns at once here.
If your original layers have different boundaries you may want to add a
region to "C" containing (at least) the difference B - C before overlaying.
To obtain a list of points and their containing polygons, use SQL Select:
Select Columns: *
from Tables: P, C
where Condition: P.obj within C.obj
As above, if you have sites outside any of your final polygons you may want
to add a region which contains them - just draw a big box and "erase" all
the other polygons from it. Otherwise your sites won't show up in the query
results.
- Scott
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