Scripting Guide - SAS

Chapter 7 Data Structures 153
Matrices
5 3 7 1,
9 9 8 8,
1 5 4 3]);
[1,3,8,3]
Calculate Diagonal Quadratic Forms
The VecQuadratic() function calculates the hats in regression that go into the standard errors of
prediction or the Mahalanobis or T2 statistics for outlier distances. Vec Quadratic(Sym, X) is
equivalent to calculating VecDiag(X*Sym*X`).The first argument is a symmetric matrix, usually an
inverse covariance matrix. The second argument is a rectangular matrix with the same number of columns
as the symmetric matrix argument.
Return the Sum of Diagonal Elements
The Trace() function returns the sum of the diagonal elements for a square matrix.
D=[0 1 2, 2 1 0, 1 2 0];
trace(D); // returns 1
Generate a Row Vector of Integers
The Index() function generates a row vector of integers from the first argument to the last argument. A
double colon :: is the equivalent infix operator.
6::10;
[6 7 8 9 10]
Index(1,5);
[1 2 3 4 5]
The optional increment argument changes the default increment of +1.
Index(0.1, 0.4, 0.1);
[0.1, 0.2, 0.3, 0.4]
The increment can also be negative.
Index(6, 0, -2);
[6, 4, 2, 0]
The default value of the increment is 1, or -1 if the first argument is higher than the second.
Reshape a Matrix
The Shape() function reshapes an existing matrix across rows to be the specified dimensions. The
following example changes the 3x4 matrix a into a 12x1 matrix:
a=[1 1 1, 2 2 2, 3 3 3, 4 4 4];
shape(a, 12, 1)
[1,1,1,2,2,2,3,3,3,4,4,4]