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I think you need to be more clear about what, exactly, you want. For certain classes of functions calculating the limit is quite involved and requires differentiation. If you want to do this for any input function then you'll need to get into symbolic manipulation. That's a project in itself. Calculating mathematical limits is not an easy task.
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Thank you all
In fact yes, I want to write a program for calculating all limits, for example Lim(sin(2/x)) when x->0, or even x->Infinite
so I must write a parser I think
but maybe I can find something that helps me how to start!
thanks
www.logicsims.ir
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Hi Hadi,
The problem is not just the parser. You will also need both a symbolic manipulation and numeric component. The symbolic package will be needed to calculate derivatives for certain limits that require l'Hopital's rule[^]. Other methods used in computer-based limit calculations are Wynn's epsilon algorithm[^] and generalized Euler transforms.
As you can see, it is a non-trivial project and requires an understanding of some rather advanced mathematics.
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Yeah, but don't black bodies absorb and then re-emit photons of the same frequency? Melanin absorbs UV and then re-emits about 99.9% of it as infra-red. How does it do THAT? Where does the rest of the energy go?
Richard A. Abbott wrote: Are you querying this because of interest in Anti-Cancer agents or ???
I dunno. Just generalised interest.
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If I can remember back 40 years to my Chemistry/Physics classes, the energentic UV hits the atoms of the Melanin and causes the electrons to jump several states (all jumps are discrete jumps of energy levels), and then the electrons drop back down one level at a time releasing the energy in the form of IR (lower frequency, lower energy). There is no extra energy, but the IR will cause an increase in temperature in the local area.
Dave.
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Ohhh, OK, so the electrons don't have to make the same sized leap all in one go. OK, that makes sense. 
[edit:] Of course, that leaves the question of how it so consistently chooses these smaller quantum-leap pathways...
modified on Sunday, November 9, 2008 2:12 AM
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Hi
thank you very much, it helps me a lot
thank you
www.logicsims.ir
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Hadi Dayvary wrote: for sure it needs a parser
Have you seen these from this CP article search[^]? The one by Hatem is a really good one.
"The clue train passed his station without stopping." - John Simmons / outlaw programmer
"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon
"Not only do you continue to babble nonsense, you can't even correctly remember the nonsense you babbled just minutes ago." - Rob Graham
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73Zeppelin wrote: Not exactly a trivial programming project.
I agree. Interesting project idea, nonetheless.
"The clue train passed his station without stopping." - John Simmons / outlaw programmer
"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon
"Not only do you continue to babble nonsense, you can't even correctly remember the nonsense you babbled just minutes ago." - Rob Graham
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Paul Conrad wrote: I agree. Interesting project idea, nonetheless.
Yes, looks like he's shooting for a Mathematica-type app. Very interesting, but quite involved - not sure if it's a single programmer project.
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73Zeppelin wrote: looks like he's shooting for a Mathematica-type app
Sounds like it.
73Zeppelin wrote: Very interesting, but quite involved - not sure if it's a single programmer project.
Yep. It would be a pretty ambitious project to do by oneself.
"The clue train passed his station without stopping." - John Simmons / outlaw programmer
"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon
"Not only do you continue to babble nonsense, you can't even correctly remember the nonsense you babbled just minutes ago." - Rob Graham
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No, it's a team work, we are working on a new math project,
we need to do this
www.logicsims.ir
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I'm not expecting a wodge of code handed to me on a plate (though I won't say no...), more of a string hint on where to go looking.
I have a set of data points (successive Y values evenly spaced along the X axis). This is crudely a flat line of 0, with a bump part of the way a long, and then some noise added. The bump could well have a flat top to it.
By eye, it's easy to work out where the peak of the underlying curve should be, but a lot less easy to just grab a crude maximum value and expect it to be useful.
From experience, the curve is pretty close to a gaussian that someone has sliced the top off of. I'm trying to find some method of writing / reusing / blatantly stealing a black box function I can give a series of Y values, and get the parameters (centre X, magnitude and 'sharpness') of a gaussian curve.
Can you give me any pointers to useful web pages you've found?
I'm not averse to writing my own, wiggling values and doing fit comparisons, but I'm sure someone made a wonderful algorithm with three names in the 70s that would be vastly superior.
Iain.
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What about least squares?
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
[My articles]
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looking for something a leeeeeeeeettle more clever!
Iain.
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Well, I never thought (never, in my naive life  ) least squares weren't clever. It's traditional, old-fashioned  statistics, I know, but it does its job.
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
[My articles]
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I owe the inventors of least squares an apology - it is clever. But it is only a method for determining how good a fit your function is to the data - it only indirectly helps you get that function.
There's nothing wrong with good old fashioned stats, but I'm looking for something more along the lines of the nice algorithm for working out a convex hull. One of those "oh, that's neat, and about a million times faster than me throwing brute force PC guesswork at the problem".
Well, maybe I'll invent that cunning method, and retire to a comfy slippered life as a CS professor.
Iain.
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Iain Clarke wrote: But it is only a method for determining how good a fit your function is to the data - it only indirectly helps you get that function.
It actually helps to find the parameters of the function, but you should make a 'a priory' (as already pointed out by 73Zeppelin) hypothesis about it. I supposed (wrongly) you were pretty confident it was a Gaussian shape.
Iain Clarke wrote: Well, maybe I'll invent that cunning method, and retire to a comfy slippered life as a CS professor.
Good luck, Prof.Clarke (it sounds good) 
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
[My articles]
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Try non-parametric kernel density estimation to fit it. That way you don't have to assume a distribution a priori.
Link[^]!
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looks promising... just need to change my question to how to do that! (or read more...)
Iain.
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Hi Iain,
Kernel density estimation is not as complicated as it sounds. You just need the two functions from the Wikipedia article I linked to. The real problem is the choice of bandwidth, h. You can actually adjust this manually - algorithms for calculating h based on your sample can be more complicated than the density estimation itself. I always adjust h by hand (well, in most cases!).
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Well, I'll be writing myself a dialog app with some self generated data later, and I'll see how well I've absorbed that page!
Should wake my brain up at the very least!
Iain.
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If you need help, post here. I keep checking this forum.
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