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The Lost Art of Logarithms

lostartoflogarithms.com

31–40 of 204 posts

Re: The Lost Art of Logarithms

#31
post #24

Here's an logarithmic fact that I've made use of frequently: If X is a random variable having a uniform distribution between zero and one, then –ln( X )/ λ has an exponential distribution with rate λ . This relationship comes in handy when, for example, you want to draw weighted random samples. Or generating event times for simulations.

How long do I have to study math to understand this?

Depends on how much you practiced high school math. It's not hard but we forget it without practice.

Re: The Lost Art of Logarithms

#32
post #24

Here's an logarithmic fact that I've made use of frequently: If X is a random variable having a uniform distribution between zero and one, then –ln( X )/ λ has an exponential distribution with rate λ . This relationship comes in handy when, for example, you want to draw weighted random samples. Or generating event times for simulations.

How long do I have to study math to understand this?

Ask chatgpt to explain it to you like you're 18. It made it really easy to understand.

Re: The Lost Art of Logarithms

#34
(I'm sure this is in the book) John Napier, the father of logarithms (the N in ln), basically had a sweatshop of human calculators making log tables over something like 20 years - critical for celestial navigation. There was a huge price attached to the person that developed a method to safely navigate across the oceans, also lead to the invention of the pocket watch

Re: The Lost Art of Logarithms

#35

Earlier quoted context omitted.

https://mathcenter.oxford.emory.edu/site/math108/logs/ Some people have suggested the "triangle of power".

The Triangle of power explanation of logarithms is what really got me across logs. It wasn't until seeing the triangle and having the relationships explained that I had any clue about logarithms, up until then logs had been some archaic number that meant nothing to me. Because of the triangle of power, I now rock up to B and B+ Trees and calculate the number of disc accesses each will require in the worst case, depen…

Ironically, that notation, which I just discovered, confuses me more than anything else. Logs clicked for me when someone online said "amongst all the definitions we have for logs, the most useful and less taught is that log() is just a power". At that exact instant, it's like if years of arcane and foreign language just disappeared in front of my eyes to leave only obviousness and poetry.

Re: The Lost Art of Logarithms

#36
I learned the multiplication using addition and a lookup table in a class taught by Huffman (of Huffman compression fame). You weren't allowed to use a calculator on the test.

But my absolute favorite trick is base conversions, https://www.khanacademy.org/math/algebra2/x2ec2f6f830c9fb89:... with some practice you can do approximate base conversions (power to 2 to power of 10 or e) in your head

Re: The Lost Art of Logarithms

#37
post #24

Here's an logarithmic fact that I've made use of frequently: If X is a random variable having a uniform distribution between zero and one, then –ln( X )/ λ has an exponential distribution with rate λ . This relationship comes in handy when, for example, you want to draw weighted random samples. Or generating event times for simulations.

How long do I have to study math to understand this?

Unless I'm missing something, this can just be directly verified, no “understanding” necessary. All you need to know is that probability distributions can be characterized by their probability density function (PDF).

If Y=-ln(X)/lambda, then P(Yexp(-lambda a)) = 1-exp(-lambda a).

And if Z is exponential with rate parameter lambda, then P(ZThey have the same PDF, so they're the same distribution.

Re: The Lost Art of Logarithms

#38
post #34

(I'm sure this is in the book) John Napier, the father of logarithms (the N in ln), basically had a sweatshop of human calculators making log tables over something like 20 years - critical for celestial navigation. There was a huge price attached to the person that developed a method to safely navigate across the oceans, also lead to the invention of the pocket watch

isn't the n in ln "natural" ("logarithm natural")?

Re: The Lost Art of Logarithms

#39
post #24

Here's an logarithmic fact that I've made use of frequently: If X is a random variable having a uniform distribution between zero and one, then –ln( X )/ λ has an exponential distribution with rate λ . This relationship comes in handy when, for example, you want to draw weighted random samples. Or generating event times for simulations.

How long do I have to study math to understand this?

Most textbooks on probability have some discussion of the relationships between the various distributions commonly in use. If you just want a quick overview, I found John D. Cook’s diagram to be handy:

https://www.johndcook.com/blog/distribution_chart/

Re: The Lost Art of Logarithms

#40
post #24

Earlier quoted context omitted.

How long do I have to study math to understand this?

I love that you asked this, but I think it's not quite the right question. I've been wishing for years that someone would maintain a "dependency graph" for mathematical concepts. I think Khan Academy tried to do something like this at one point but took it down a long time ago. As long as we're far enough from the bleeding-edge of research topics, I feel like maths is the one field where this might be possible to do…

That's more-or-less the purpose of https://mathworld.wolfram.com/ or at least, it's significantly better at it than, say, wikipedia.
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