Usage Note 33029: BY-group processing in PROC IML
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You can perform BY-group processing in PROC IML by making use of the UNIQUEBY function and a DO loop.
The UNIQUEBY function returns the locations of the unique BY-group combinations for a sorted or indexed matrix. If the matrix is not sorted then use the SORT function prior to the UNIQUEBY function. With the vector that it returns, you can use the subscript operator, [ ], to perform operations on each of the unique BY groups.
The example below shows how this can be done. The POTTERY data set has four BY groups defined by the variable SITE.
data pottery;
input Site X Fe Mg Ca Na;
datalines;
1 14.4 7.00 4.30 0.15 0.51
1 13.8 7.08 3.43 0.12 0.17
1 14.6 7.09 3.88 0.13 0.20
1 11.5 6.37 5.64 0.16 0.14
1 13.8 7.06 5.34 0.20 0.20
1 10.9 6.26 3.47 0.17 0.22
1 10.1 4.26 4.26 0.20 0.18
1 11.6 5.78 5.91 0.18 0.16
1 11.1 5.49 4.52 0.29 0.30
1 13.4 6.92 7.23 0.28 0.20
1 12.4 6.13 5.69 0.22 0.54
1 13.1 6.64 5.51 0.31 0.24
1 12.7 6.69 4.45 0.20 0.22
1 12.5 6.44 3.94 0.22 0.23
2 11.8 5.44 3.94 0.30 0.04
2 11.6 5.39 3.77 0.29 0.06
3 18.3 1.28 0.67 0.03 0.03
3 15.8 2.39 0.63 0.01 0.04
3 18.0 1.50 0.67 0.01 0.06
3 18.0 1.88 0.68 0.01 0.04
3 20.8 1.51 0.72 0.07 0.10
4 17.7 1.12 0.56 0.06 0.06
4 18.3 1.14 0.67 0.06 0.05
4 16.7 0.92 0.53 0.01 0.05
4 14.8 2.74 0.67 0.03 0.05
4 19.1 1.64 0.60 0.10 0.03
;
This PROC MEANS step uses BY-group processing to compute the sums of variables X and FE.
proc means sum;
by site;
var x fe;
run;
The following IML code reproduces the results of the preceding PROC MEANS step using the UNIQUEBY function to perform BY-group processing. These statements invoke PROC IML and read the SITE, X, and FE variables from the POTTERY data set into a matrix named A:
proc iml;
use pottery;
read all var{site x fe} into a;
In these statements you should not need to change anything other than the matrix name.
unique_rows=uniqueby(a,1,1:nrow(a));
do i=1 to nrow(unique_rows);
/* Next line is for the last BY group */
if i=nrow(unique_rows) then index=unique_rows[i]:nrow(a);
else index=unique_rows[i]:unique_rows[i+1]-1;
submat=a[index,];
Below is where you put your function. This particular example computes the sum for X and FE in each BY group.
sum=sum//submat[+,2:3];
end;
print sum;
quit;
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Operating System and Release Information
| Product Family | Product | System | SAS Release | |
| Reported | Fixed* | |||
| SAS System | SAS/IML | z/OS | ||
| OpenVMS VAX | ||||
| Microsoft® Windows® for 64-Bit Itanium-based Systems | ||||
| Microsoft Windows Server 2003 Datacenter 64-bit Edition | ||||
| Microsoft Windows Server 2003 Enterprise 64-bit Edition | ||||
| Microsoft Windows XP 64-bit Edition | ||||
| Microsoft® Windows® for x64 | ||||
| OS/2 | ||||
| Microsoft Windows 95/98 | ||||
| Microsoft Windows 2000 Advanced Server | ||||
| Microsoft Windows 2000 Datacenter Server | ||||
| Microsoft Windows 2000 Server | ||||
| Microsoft Windows 2000 Professional | ||||
| Microsoft Windows NT Workstation | ||||
| Microsoft Windows Server 2003 Datacenter Edition | ||||
| Microsoft Windows Server 2003 Enterprise Edition | ||||
| Microsoft Windows Server 2003 Standard Edition | ||||
| Microsoft Windows XP Professional | ||||
| Windows Millennium Edition (Me) | ||||
| Windows Vista | ||||
| 64-bit Enabled AIX | ||||
| 64-bit Enabled HP-UX | ||||
| 64-bit Enabled Solaris | ||||
| ABI+ for Intel Architecture | ||||
| AIX | ||||
| HP-UX | ||||
| HP-UX IPF | ||||
| IRIX | ||||
| Linux | ||||
| Linux for x64 | ||||
| Linux on Itanium | ||||
| OpenVMS Alpha | ||||
| OpenVMS on HP Integrity | ||||
| Solaris | ||||
| Solaris for x64 | ||||
| Tru64 UNIX | ||||
| Type: | Usage Note |
| Priority: | |
| Topic: | Analytics ==> Matrix Programming Data Management ==> Manipulation and Transformation ==> BY-group processing SAS Reference ==> Procedures ==> IML |
| Date Modified: | 2008-08-22 14:42:22 |
| Date Created: | 2008-08-21 10:19:12 |