```Date: Mon, 26 Oct 2009 09:41:45 -0400 Reply-To: Chao Yawo Sender: "SAS(r) Discussion" From: Chao Yawo Subject: Need Help Creating a Matrix Content-Type: text/plain; charset=ISO-8859-1 Hi, I have a dataset with the following structure. ColumnA ColumnB ColumnC ClassA OtherStud WorkWith AA DD 1 AA EE 0 AA BB 1 BB FF 1 BB GG 1 BB KK 0 CC AA 1 CC BB 1 ColumnA refers to students in ClassroomA, and Column B refers to "Other Students" in the school who could act as work and/or playmates. Note, ColumnB could also include some of the same students in ColumnA(ClassA) who work with each other (For example, Students: AA and BB). If a Student in Classroom A works with a student in ClassroomB, ColumnC takes the value of 1, and 0(zero) if otherwise So, looking at ColumnA, we find that there are three students: AA, BB and CC. Student_AA for instance interacts with three students but only works with DD and BB. Similarly, Student_CC interacts with two students and works and plays with each of them. Now, I am interested in constructing a matrix indicating which students in ClassroomA work with each other. This means that student_AA for instance works with student_BB, who is in his/her classroom, hence the cell in their matrix will have a "1". Again, Student_CC in ClassroomA works with 2 other members of his/her own class. So CC would have two "1s" in the matrix. The resulting matrix for the "Works With" relation (ColumnC) among the 3 students in ClassroomA would look like this. AA BB CC AA 0 1 0 BB 0 0 0 CC 1 1 0 This matrix is the output I am interested in, and need to produce for the relationship specified in Column C. I would certainly appreciate some ideas to help me produce this. Thanks in advance for your assistance. Sincerely, Cy ------------------------------------------------------------------ ```

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