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GNU Octave Manual Version 3
by John W. Eaton, David Bateman, Søren Hauberg
Paperback (6"x9"), 568 pages
ISBN 095461206X
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14.1.4 Rational Approximations

Function File: s = rat (x, tol)
Function File: [n, d] = rat (x, tol)

Find a rational approximation to x within tolerance defined by tol using a continued fraction expansion. E.g,

rat(pi) = 3 + 1/(7 + 1/16) = 355/113
rat(e) = 3 + 1/(-4 + 1/(2 + 1/(5 + 1/(-2 + 1/(-7))))) 
       = 1457/536

Called with two arguments returns the numerator and denominator separately as two matrices.

See also rats

Built-in Function: rats (x, len)
Convert x into a rational approximation represented as a string. You can convert the string back into a matrix as follows:

r = rats(hilb(4));
x = str2num(r)

The optional second argument defines the maximum length of the string representing the elements of x. By default len is 9.

See also format, rat

ISBN 095461206XGNU Octave Manual Version 3See the print edition