Cases prefixed with W are classified as warnings and
do not generate an error of type NAG:error_n. See nag_issue_warnings.
The function has been called with an argument too large in absolute magnitude. There is a danger of overflow. The result returned is the value of at the nearest valid argument.
An unexpected error has been triggered by this routine. Please
Your licence key may have expired or may not have been installed correctly.
Dynamic memory allocation failed.
If and are the relative errors in the argument and result, respectively, then in principle
That is, the relative error in the argument, , is amplified by a factor, at least . The equality should hold if is greater than the machine precision ( is due to data errors etc.) but if is simply a result of round-off in the machine representation of then it is possible that an extra figure may be lost in internal calculation round-off.
The behaviour of the error amplification factor is shown by the following graph:
It should be noted that near where this amplification factor tends to zero the accuracy will be limited eventually by the machine precision. Also for
where is the absolute error in the argument .
This example reads values of the argument from a file, evaluates the function at each value of and prints the results.
fprintf('s10ac example results\n\n');
x = [-10 -0.5 0 0.5 25];
n = size(x,2);
result = x;
[result(j), ifail] = s10ac(x(j));
disp(' x cosh(x)');
s10ac example results
PDF version (NAG web site, 64-bit version, 64-bit version)