ps  If you'd like to see the patterns in the variables that are either in common or unique to a group you can add two variables to GPLUS... data gplus (keep=common nocomm group: var:); length varc varn $50; set g (rename=(group=group1)) nobs=howmany; array x(6); do j=_n_ + 1 to howmany;    set g (rename=(x1-x6=y1-y6 group=group2)) point=j;    array y(6);    do k=1 to 6;      common + (x(k)+y(k) eq 2);   if (x(k)+y(k) eq 2) then varc = catt(varc,k);      nocomm + (x(k)+y(k) eq 1);   if (x(k)+y(k) eq 1) then varn = catt(varn,k);    end; output; call missing(common,nocomm,varc,varn); end; run; patterns (for example, variable X4 shows up 7 times in both pairwise groups while variable X6 shows up 10 times in only of of the groups) ... varc    Frequency     Percent ----------------------------- 14             3       33.33 2              2       22.22 24             1       11.11 4              2       22.22 56             1       11.11    Frequency Missing = 12 varn     Frequency     Percent ------------------------------ 1               1        5.26 12              2       10.53 1234            2       10.53 12456           2       10.53 134             1        5.26 1456            4       21.05 2               2       10.53 2356            2       10.53 2456            2       10.53 34              1        5.26     Frequency Missing = 2 disclaimer ... Then again, this might all be possible in some of the PROCs suggested by others. ... View more

Hi, addressing just the "in common" question (as in  "Groups 6 &7 have 2 in common, 1 not in common") ... easier to work with variable scheme X1-X6 rather than names, data step seems like a lot easier way to make a simple data set ... data g; infile datalines dsd; input  group :$1. x1-x6; datalines; 1,0,1,1,0,0,0 2,0,0,0,0,1,1 3,0,0,0,0,1,1 4,1,0,0,1,0,0 5,1,0,0,1,0,0 6,1,1,0,1,0,0 7,0,1,0,1,0,0 ; data gplus (keep=common nocomm group:); set g (rename=(group=group1)) nobs=howmany; array x(6); do j=_n_ + 1 to howmany;    set g (rename=(x1-x6=y1-y6 group=group2)) point=j;    array y(6);    do k=1 to 6;      common + (x(k)+y(k) eq 2);      nocomm + (x(k)+y(k) eq 1);    end; output; call missing(common,nocomm); end; run; output ... Obs    group1    group2    common    nocomm   1      1         2          0         4   2      1         3          0         4   3      1         4          0         4   4      1         5          0         4   5      1         6          1         3   6      1         7          1         2   7      2         3          2         0   8      2         4          0         4   9      2         5          0         4 10      2         6          0         5 11      2         7          0         4 12      3         4          0         4 13      3         5          0         4 14      3         6          0         5 15      3         7          0         4 16      4         5          2         0 17      4         6          2         1 18      4         7          1         2 19      5         6          2         1 20      5         7          1         2 21      6         7          2         1 (idea for second data step from Tom's recent posting for question on how to "Create Vector"  in SAS Macro Facility, Data Step and SAS Language Elements ... thanks) ... View more

Hi, another idea ... data want (keep = id tot:); array tot(12); do j=1 to 12; tot(j)=0; end; do until(last.id);    set have;    by id;    k = 3 * (ceil(group_var/25) + (group_var eq -50) + 1);    tot(k+1) + count_var1;    tot(k+2) + count_var2;    tot(k+3) + count_var3; end; run; ID    tot1    tot2    tot3    tot4    tot5    tot6    tot7    tot8    tot9    tot10    tot11    tot12 1      2       2       8       2       0       1       5       3       2       0        0        0 2      1       2       3       3       4       3       0       0       0       0        0        0 ... View more

Hi ... maybe get rid of the error messages in the LOG ... data c;   set b;   set a key=x;   if ^_error_ then output; else _error_ = 0; run; ... View more

Hi, a more prolix approach than the SQL idea (assumes variable in LOOKUP is named same as in MAIN, i.e. KEY_VAR)... data main; retain oth_var 'xxx'; declare hash h(dataset: "lookup"); h.defineKey('key_var'); h.defineData('oth_var'); h.definedone(); do until (last);   set main end=last;   if categ_var eq 'A' then h.find();   output;   call missing(oth_var); end; stop; run; ... View more

Hi.  The OUTER loop rules.  There's one pass through the data step since all the observations in the data set are read within the loop.  The data step still returns to the beginning one more time to see if there are any more observations to be read.  Since there are none, the data step is finished.  You can see that by modifying the code as follows and looking at the LOG (you'll see two AT START and one AT END) ... data even; PUT "AT START"; do _n_=1 to howmany;   set all nobs=howmany;   if ^mod(x,2) then output; end; PUT "AT END"; run; However, there's really no reason to do what I did in my example.  Without the outer do loop, the data step would work the same way.  I only did that to show you that even though the SET statement with NOBS=HOWMANY occurs after the start of the loop that uses the variable HOWMANY, the loop still works (example of what happens prior to execution versus what happens during execution of a data step). One situation where you might use actually use a loop within a data step is that it's one way to separate statements that need only to be executed once rather than on each pass through the data step.  The execute once statements occur outside the loop while those executed as each observation is read occur within the loop. Another great use of loops to read data is the DOW, especially handy when looking at groups of observations with your data with BY-GROUP processing.  If you don't know about the DOW, there's no need to explain it here since there are a number of really good papers to read ... HOW to DOW (if you have never read a Paul Dorfman paper, it's a treat) http://support.sas.com/resources/papers/proceedings12/156-2012.pdf an earlier version of some material in the above ... The DOW-Loop Unrolled (another one by Paul Dorfman, why not read the best) http://analytics.ncsu.edu/sesug/2007/SD08.pdf The above includes the following which is what I meant by isolating the repeated execution of some statements from others to be executed once ... The DOW-loop (Whitlock DO-loop) is a nested repetitive DATA step programming structure, intentionally organized in order to allow for programmatically and logically natural isolation of DO-loop instructions related to a certain break-event from actions performed before and after the loop, and without resorting to superfluous conditional statements. Just search for "SAS DOW" and you'll find more. ... View more

And about this ... /* not sure about using compsum before it is defined */ if compsum = 0 then no_comps = 1; compsum = sum(comp1, comp2, comp3); The statement with the SUM function is just an assignment statement (and not at all DANGEROUS) ... as explained in on-line HELP ... Syntax variable=expression; Arguments variable names a new or existing variable. Range variable can be a variable name, array reference, or SUBSTR function. Tip Variables that are created by the Assignment statement are not automatically retained. expression is any SAS expression. Tip expression can contain the variable that is used on the left side of the equal sign. When a variable appears on both sides of a statement, the original value on the right side is used to evaluate the expression, and the result is stored in the variable on the left side of the equal sign. For more information, see Expressions in SAS Language Reference: Concepts. Prior to the assignment statement, the value of COMPSUM is MISSING, not 0 so NO_COMPS is never assigned a value. This works fine ... data fin; set raw; compsum = sum(of comp:); run; Values on the RIGHT of the = are known (variables or constants).  Values on the LEFT of the = can be new or already known variables.  If you are still squeamish about declaring variables, you could always assign an initial value in a RETAIN statement (DECLARATIVE, happens once, not EXECUTABLE) ... retain comp_sum 0; A RETAIN statement has other consequences, but in your case you are assigning a new value with every pass through the data step and the retaining of the variable value is of no consequence. ... View more

Hi ... one comment on your statement  "The variable nobs_doctors is used in the do loop before the set statement in which it is declared." This is related to COMPILE versus EXECUTION and this works fine ... data all; input x @@; datalines; 1 2 3 4 5 6 7 8 9 10 ; data even; do _n_=1 to howmany;   set all nobs=howmany;   if ^mod(x,2) then output; end; run; since a value is assigned to the variable HOWMANY prior to data step execution. ... View more

As Doc implied, that's seems like an easy question but it really isn't.  If you are at the point of " I think I remember reading that the data step does some pre-processing <more>", I think you should look at ... "Executable and Declarative Statements" ... SAS(R) 9.3 Statements: Reference ... to get some understanding of what can be done during data step execution versus what occurs prior to execution.  There's a classic paper (a bit dated but still worth a read) "The SAS Supervisor" ... http://www.lexjansen.com/nesug/nesug88/sas_supervisor.pdf ... that has a great explanation as to what happens prior to and at execution of a data step. Also worth a look is "DATA Step Statements by Category" ... SAS(R) 9.3 Statements: Reference ... View more

Hi, one more idea ... data y; retain header3 '2015-2014(difference)'; do j=1 to howmany;    set x (drop=header3) nobs=howmany point=j;    j+1;    set x (drop=header3 rename=(header5=_n_)) point=j;    header5 = header5 - _n_;    output; end; stop; run; ... View more