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# Create column of Re-indexed month values based on macro value 12 months back

[ Edited ]

Hello All,

I have some code that I update each month for work that calculates a number of statistics over the last 12 months of shippment data for a number of different shipment groups i.e. plane, train, truck, ship etc.

In short, I have a column named shipment date which spans around 100 thousand rows and repeats the values 1-12 specifiying the month and another column named shipment count which gives the number of shipments on that date which looks something like this:

```data shipments
input Shipment_Month Shipment Count;
datalines;
1 22 33 54 65 76 97 108 119 1210 1111 812 71 .2 .3 .4 .. .. .. .. .. .```

Each time I run the code there are two macro variables that update which give me the end of last month and the beggining of the month 12 months ago (spans 12 months). What i'd like to do is just create a column called Shipment_reindex which is populated by reindexed values 1-12 from the Shipment_Month column with the value of the macro that gives me 12 months back i.e. month(&Back_12_Months) = 5 rei-indexed to 1 and so on i.e. 5=1, 6=2, 7=3, 8=4, 9=5, 10=6, 11=7, 12=8, 1=9, 2=10, 3=11, 4=12.

```Shipment_Month Shipment_Count Shipment_reindex
1              2                  9    2              3                 10    3              5                 11    4              6                 12                  5              7                  1    6              9                  2    7             10                  3    8             11                  4    9             12                  5   10             11                  6   11              8                  7   12              7                  8   1               .                  9   2               .                 10   3               .                 11   4               .                 12   5               .                  1   .               .```

I can think of the hard way to do it:

if Shipment_Month=5 then shipment_Reindex=1;

else if Shipment=6 then Shipment_Reindex=2

....

But i'd like for it to update the column automatically when I run the code instead of me constantly having to change the values. I've been messing around with arrays, but am getting nowhere fast.

Thanks,

- Keith

PROC Star
Posts: 8,165

## Re: Create column of Re-indexed month values based on macro value 12 months back

Couldn't you just include some code (or a macroized version of the following code) like:

```data want (keep=shipment_date Shipment_Reindex);
input shipment_date date9.;
if month(shipment_date) lt month(today()) then
month1=mdy(month(shipment_date),1,year(today())+1);
else month1=mdy(month(shipment_date),1,year(today()));
month2=today();
Shipment_Reindex=intck('month',month2,month1)+1;
cards;
12may2015
10dec2016
15mar2017
;
```

Art, CEO, AnalystFinder.com

New Contributor
Posts: 3

## Re: Create column of Re-indexed month values based on macro value 12 months back

HI,

`DATA shipments2;SET shipments;IF eof1=0 THEN DO; SET shipments(firstobs=4  KEEP=Shipment_Month Shipment_Count  RENAME=(Shipment_Month=lead_Shipment_Month Shipment_Count=lead_Shipment_Count))  end=eof1;END;ELSE DO; lead_Shipment_Month=.; lead_Shipment_Count=.;END;lag_Shipment_Month=lag4(Shipment_Month);lag_Shipment_Count=lag4(Shipment_Count);RUN;`

Posts: 4,736

## Re: Create column of Re-indexed month values based on macro value 12 months back

If I understand your process and requirement correctly then below should do the job.

``````/* data after appending latest month */
data have;
format shipment_date date9.;
do shipment_date="01Apr2015"d to "31Mar2017"d;
Shipment_Month=month(shipment_date);
Shipment_reindex=month(shipment_date);
output;
end;
run;

/* determine latest shipment_date in table */
proc sql noprint;
select max(shipment_date) into :max_shipment_date
from have
;
quit;

/* update Shipment_reindex using latest shipment_date in table */
proc sql;
update have
set
Shipment_reindex= 12-mod(intck('month',shipment_date,&max_shipment_date),12)
;
quit;
``````
Posts: 4,736

## Re: Create column of Re-indexed month values based on macro value 12 months back

@siope1kd

The following is a bit more involved but it would allow you to apply the new "index" on-the-fly without a need to update your table.

The code uses a format on column "shipment_reindex". The specialty is that the format itself encapsulates the function which does the actual calculation. The only thing you would need to do on a monthly basis is to update the function instead of all the values in your have table.

Actually: You wouldn't even need an extra column "shipment_reindex" but you just apply the format to column "shipment_date" whenever you need it.

Sample code below:

``````/* data after appending latest month */
data have;
format shipment_date date9.;
do shipment_date="01Apr2015"d to "31Mar2017"d;
Shipment_Month=month(shipment_date);
Shipment_reindex=shipment_date;
output;
end;
run;

/* determine latest shipment_date in table */
proc sql noprint;
select max(shipment_date) into :max_shipment_date
from have
;
quit;

/* recreate function using &max_shipment_date */
proc fcmp outlib=sasuser.funcs.myfuncs;
function shipment_reindex(in_date) ;
month_index = 12-mod(intck('month',in_date,&max_shipment_date),12);
return (month_index);
endsub;
run;

options cmplib=(sasuser.funcs);

proc format lib=sasuser;
value _shipment_reindex
other=[shipment_reindex()];
run;

/* apply format to dataset have */
proc datasets lib=work;
modify have;
format Shipment_reindex _shipment_reindex2.
;
run;
quit;
``````

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