Hi I am having a problem with processing an array but I just can't seem to get it using a simple loop. Essentially I am trying to get a week weekly count from cumulative value given for week. So for example the weekly value for week #10 I want would be Week #10 - Week#9. Using the Macro processor there is no problem with the loop however with a the do loop in the data step I get an "array subscript out of range" error.    data producer_shipments13; set pcars13."Sheet1$"n; Array Week {53} week0-week52; Array PCarUnl {52} PCarUnl1 - PCarUnl52;     do I=1 to 52;         lastWeek=I-1;         PCarUnl{i} = Week{i} - Week{lastWeek}; end; run;   It would appear that the error is occuring at start of the loop and if I change my loop to start at 2, and make my PCarUnl array 1 column larger I get what I need with a couple of null columns to clean up. data producer_shipments13; set pcars13."Sheet1$"n; Array Week {53} week0-week52; Array PCarUnl {53} PCarUnl0 - PCarUnl52;     do I=2 to 52;         lastWeek=I-1;         PCarUnl{i} = Week{i} - Week{lastWeek}; end;   run;   I would have assumed this is a Program Data Vector thing for row prcessing but not so confident on how things work in arrays. Any array mavens out there who care explain or have a link that I can read through on what is happening.   Many Thanks,   Kevin      ... View more