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function P = pei(n, alpha, classname) %PEI Pei matrix. % GALLERY('PEI',N,ALPHA), where ALPHA is a scalar, is the symmetric % matrix ALPHA*EYE(N) + 1. The default for ALPHA is 1. % The matrix is singular for ALPHA = 0, -N. % Reference: % M. L. Pei, A test matrix for inversion procedures, Comm. ACM, % 5 (1962), p. 508. % % Copyright 1984-2013 The MathWorks, Inc. if isempty(alpha) alpha = 1; end P = alpha*eye(n,classname) + 1;