## Average of last x entries in each column of a triangle

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Posts: 261

# Average of last x entries in each column of a triangle

Period123456
.....................
20140122223303034000080000123444144000
2014022233440002100202120000132000.
201403129934150000123444130000..
2014045434975000123444...
20150199900134423....
201502102030.....

I have created triangles of data in SAS. When I say triangles, the cells off the triangle are left blank. The actual triangle is much bigger than this one and I'm trying to write the code to sum over the bottom nonblank cells of each column. I'm not sure if this is possible but I would think it would involve proc summary.

Are there any functions that can achieve this?

Thank you

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Solution
‎08-05-2015 06:39 AM
Super User
Posts: 9,599

## Re: Average of last x entries in each column of a triangle

Hi,

You could use arrays:

data want;

set have;

array var{6};  /* I assume your variables are prefixed with var */

do i=1 to 6;

if var{i}=. then do;

do j=i-1 to 1 by -1;

result=sum(result,var{j});

end;

leave;

end;

end;

run;

So the above looks for the last record (i.e. the first .), then takes the previous numbers and sums them up.  You could do mean of certain, e.g. change the to 1 to 3, and mean is just sum / i-1.

All Replies
Solution
‎08-05-2015 06:39 AM
Super User
Posts: 9,599

## Re: Average of last x entries in each column of a triangle

Hi,

You could use arrays:

data want;

set have;

array var{6};  /* I assume your variables are prefixed with var */

do i=1 to 6;

if var{i}=. then do;

do j=i-1 to 1 by -1;

result=sum(result,var{j});

end;

leave;

end;

end;

run;

So the above looks for the last record (i.e. the first .), then takes the previous numbers and sums them up.  You could do mean of certain, e.g. change the to 1 to 3, and mean is just sum / i-1.

Super Contributor
Posts: 261

## Re: Average of last x entries in each column of a triangle

Thanks RW9

That works when summing the last 6 cells on a row but I wanted to get the average of the last 8 nonzero cells on each column. The length of the triangle is 36*36 so I want to take the average of the last 8.

Using the above example (and assuming I only want the average of the last 2 non-zero cells I would want

(102030+99900)/2 = 100965

(134423+75000)/2 = 104711.5

(123444+123444)/2 = 123444

(130000+120000)/2 = 125000

(132000+123444)/2 = 127722

144000 (where there are less than the number we want to get to average over it just gets the average of what's there|).

Posts: 3,852

## Re: Average of last x entries in each column of a triangle

Seems like a job for STAT functions more that array loops to me.

data tri;
infile cards4 dsd missover;

input period:yymmn. var1-var6;
format period yymmn.;

cards;
201401,22223,30303,40000,80000,123444,144000
201402,22334,40002,100202,120000,132000,.
201403,129934,150000,123444,130000,.,.
201404,54349,75000,123444,.,.,.
201501,99900,134423,.,.,.,.
201502,102030,.,.,.,.,.
;;;;
run;
proc print;

run;
data trisum;
set tri;
array v
• var:;
•    n = n(of v
• );

• if n lt dim(v) then x = sum(of v
• );
•    run;
proc print;

run;

Super Contributor
Posts: 261

## Re: Average of last x entries in each column of a triangle

I ended up using this but it's a bit messy...

data average;
input key \$4.;
datalines;
mean
run;

%macro average;

%do j = 0 %to 36;

data test&j;
set test;
if qtr&j = . then delete;
key = "mean";
keep key qtr&j;
run;

data test&j;
set test&j(obs=10);
run;

proc summary data = test&j nway missing;
class key;
var  qtr&j;
output out = test&j(drop = _freq_ _type_) mean=;
run;

data average;
merge average test&j;
by key;
run;

%end;
%mend;

%average;

Posts: 3,852

## Re: Average of last x entries in each column of a triangle

I don't understand what you want.  For the data you show what values are summed?   You imply there is more than one upper triangular matrix, if so show example and if there is variable to differentiate.

data _null_;

x = sum(144000,132000,130000,123444,134423,102030);
put x=;
run;

x=765897
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