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| Re: Inverse hyperbolics? [message #85812 is a reply to message #85811] |
Wed, 11 September 2013 09:34   |
suicidaleggroll
Messages: 14
Registered: September 2013
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Junior Member |
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On Wednesday, September 11, 2013 10:14:43 AM UTC-6, Mark Piper wrote:
> On Wednesday, September 11, 2013 4:48:48 AM UTC-6, Tom Grydeland wrote:
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>> Will these be in IDL anytime soon? I'm amazed they're not.
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>> (Yes, I have the implementation from MGLib)
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>> If you need a reason, look no further than http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_c oordinate_system
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>> --T
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> This is a very reasonable request. While we're at it, maybe we should add secant, cosecant and cotangent functions. And a log base 2 function. Here's the list of transcendental functions currently in IDL:
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> http://www.exelisvis.com/docs/routines-65.html
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> Any others?
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> mp
For log base 2 (or any other base), just make your own function:
function alogn, x, n
return, alog(x)/alog(n)
end
And secant, cosecant, cotangent are even easier. Just more 1-liners.
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| Re: Inverse hyperbolics? [message #85813 is a reply to message #85812] |
Wed, 11 September 2013 09:55 |
Mark Piper
Messages: 198
Registered: December 2009
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Senior Member |
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On Wednesday, September 11, 2013 10:34:21 AM UTC-6, suicida...@gmail.com wrote:
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> For log base 2 (or any other base), just make your own function:
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> function alogn, x, n
> return, alog(x)/alog(n)
> end
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> And secant, cosecant, cotangent are even easier. Just more 1-liners.
True, but why should a user have to go through an extra step? These functions should just be included, as a convenience, in IDL.
mp
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| Re: Inverse hyperbolics? [message #85817 is a reply to message #85815] |
Wed, 11 September 2013 14:20 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Huh, that is weird. If you've got ALOG in the list of transcendentals,
why not its "inverse"?
BTW, this is a side issue, I've always wondered why the logarithm
function is called ALOG instead of just LOG.
cheers,
paulv
On 09/11/13 15:28, fawltylanguage@gmail.com wrote:
> On Wednesday, September 11, 2013 6:14:43 PM UTC+2, Mark Piper wrote:
>
>> This is a very reasonable request. While we're at it, maybe we
>> should add secant, cosecant and cotangent functions. And a log base
>> 2 function. Here's the list of transcendental functions currently
>> in IDL:
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>> http://www.exelisvis.com/docs/routines-65.html
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> exp? :-)
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> (It is there under Math Miscellaneous, but why there?)
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> regards, Lajos
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| Re: Inverse hyperbolics? [message #85826 is a reply to message #85811] |
Thu, 12 September 2013 02:58 |
tom.grydeland
Messages: 51
Registered: September 2012
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Member |
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On Wednesday, September 11, 2013 6:14:43 PM UTC+2, Mark Piper wrote:
> This is a very reasonable request.
Glad you think so! :-)
> While we're at it, maybe we should add secant, cosecant and cotangent functions.
... and their hyperbolic counterparts?
> And a log base 2 function.
Certainly.
> http://www.exelisvis.com/docs/routines-65.html
> Any others?
We've found that an 'EXPI' function, returning 'COMPLEX(COS(X), SIN(X))', would give a significant improvement in performance over 'EXP(I*X)' for a real argument.
> mp
--T
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