On 2015-04-13 20:14, Alexander Belopolsky wrote:
On Mon, Apr 13, 2015 at 2:05 PM, Chris Barker <chris.bar...@noaa.gov <mailto:chris.bar...@noaa.gov>> wrote: However, different UTC times may map to the same wall time and some expressible wall times are not results of a map of any UTC time. got it. I suggest you perhaps word it something like: wall_time = f( location, utc_time) and utc_time = f( location, utc_time ) These are two different problems, and one is much harder than the other! (though both are ugly!) You probably meant "utc_time = f( location, wall_time)" in the last equation, but that would still be wrong. A somewhat more correct equation would be utc_time = f^(-1)( location, wall_time) where f^(-1) is the inverse function of f, but since f in not monotonic, no such inverse exists.
Don't you mean "f⁻¹"? :-)
Finding the inverse of f is the same as solving the equation f(x) = y for any given y. If f is such that this equation has only one solution for all possible values of y then an inverse exists, but this is not so in our case.
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