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...e distance between each item. What I want to look at, basically, is a map with cities on it but all I have is city pairs with distances between them. How do I go between the pairs of items with distances to a two dimensional map. some sample data follows >From To Distance ItemA ItemA 0 ItemA ItemB 54 ItemA ItemC 43 ItemA ItemD 47 ItemA ItemE 44 ItemA ItemF 63 ItemA ItemG 35 ItemA ItemH 44 ItemA ItemI 43 ItemA ItemJ 79 ItemB ItemA 54 ItemB ItemB 0 ItemB ItemC 55 ItemB ItemD 61 ItemB ItemE 65 ItemB ItemF 72 ItemB ItemG 49 ItemB ItemH 57 ItemB ItemI 54 ItemB ItemJ 68 ItemC ItemA 43 ItemC ItemB...

...like to try and duplicate in the R world.  It involved creating an aggregate table of the top (n)  orders for an item by sum of cost over a select period of time.   So, take the following example :   group <- c(rep(1,10), rep(2,10), rep(3,10)) product <- c(rep("itema", 4), rep("itemb", 2), rep("itemc", 1), rep("itemc" , 3), rep("itema", 4), rep("itemb", 2), rep("itemc", 1), rep("itemc", 3),rep("itema", 4), rep("itemb", 2), rep("itemc", 1), rep("itemc", 3)) cost <- round (...

Hi all, I''m confused about how migrations work. I''ve been using them for a couple of weeks but haven''t had any serious rollback issues yet. Just now I added a field to a table with a migration and ran "rake migrate", which added the field as expected. This was in the file db/migrate/007_mymigration.rb, making it version 7. Later I changed my mind and