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MATLAB Mathematics - SERC - Index of

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1 Matrices and Linear Algebra<br />

Vector and Matrix Norms<br />

The p-norm <strong>of</strong> a vector x<br />

x p<br />

=<br />

⎛Σ x p⎞ 1 ⁄ p<br />

⎝ i ⎠<br />

is computed by norm(x,p). This is defined by any value <strong>of</strong> p > 1, but the most<br />

common values <strong>of</strong> p are 1, 2, and ∞ . The default value is p = 2, which<br />

corresponds to Euclidean length:<br />

v = [2 0 -1];<br />

[norm(v,1) norm(v) norm(v,inf)]<br />

ans =<br />

3.0000 2.2361 2.0000<br />

The p-norm <strong>of</strong> a matrix A,<br />

A p<br />

=<br />

max<br />

x<br />

Ax<br />

-------------- p<br />

x p<br />

can be computed for p = 1, 2, and ∞ by norm(A,p). Again, the default value is<br />

p = 2.<br />

C = fix(10*rand(3,2));<br />

[norm(C,1) norm(C) norm(C,inf)]<br />

ans =<br />

19.0000 14.8015 13.0000<br />

1-12

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