standard square root computation requires an iteration. Spencer
Peter Dalgaard wrote:
Mads Jeppe Tarp-Johansen wrote:
To R-helpers,
R offers the polyroot function for solving mentioned equations iteratively.
However, Dr Math and Mathworld (and other places) show in detail how to
solve mentioned equations non-iteratively.
Do implementations for R that are non-iterative and that solve mentioned
equations exists?
As far as I know, we don't even have the quadratic...
They can't be hard to implement, though. However, you may need to take
care that non-iterative solutions are not necessarily more precise or
even faster than iterative ones. There may be cancellation issues and
the closed-form expressions can be complicated and involve slow function
calls.
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