Lotfi Zadeh has died • Hacker News Board

Re: Lotfi Zadeh has died

#11

Post by dmargol1 » Sun, Sep 10, 2017, 8:58 PM UTC

throwaway613834 wrote: post #6

protomyth wrote: post #2

Darnit. Fuzzy sets and logic just made sense to me in so many ways and I found his writings quite interesting. RIP.

Would you mind concisely explaining one example and application of it? I've read (for example) about possibility theory, but I hardly understand what it helps us do that probability theory didn't.

Both are ways of dealing with uncertainty, but probability theory is more about the uncertainty around which state a variable has, while fuzzy theory is the uncertainty around the states themselves.

Let's say you have are taking a shower with an automated temperature control. The current temperature is set to 28 degrees Celsius, but there is a sudden shift to 24 degrees.

Probability Theory: Based on prior knowledge, I know that a temperature of 24 degrees Celsius is considered "hot" 10% of the time, "warm" 50% of the time, and "cold" 40% of the time. Based on this the current expected value of the probability distribution is still "warm", so I will leave it same until cold > warm.

Fuzzy Theory: Based on my fuzzy set membership, 24 degrees Celsius has 25% membership in the "hot" set, 60% membership in the "warm" set, and 50% membership in the "cold" set. My fuzzy system is setup to maintain a particular relationship between cold and hot (let's say, cold == hot), and therefore increases temperature until balanced.

Re: Lotfi Zadeh has died

#12

Post by jacquesm » Sun, Sep 10, 2017, 9:17 PM UTC

throwaway613834 wrote: post #6

protomyth wrote: post #2

Darnit. Fuzzy sets and logic just made sense to me in so many ways and I found his writings quite interesting. RIP.

Would you mind concisely explaining one example and application of it? I've read (for example) about possibility theory, but I hardly understand what it helps us do that probability theory didn't.

http://dspace.iimk.ac.in/bitstream/handle/2259/262/Fuzzy+log...

Is one sample of a fuzzy logic based controller of an industrial process. There are many such examples, I have a book here on fuzzy logic that details a whole raft of them.

Re: Lotfi Zadeh has died

#13

Post by [deleted] » Sun, Sep 10, 2017, 9:29 PM UTC

ceyhunkazel wrote: post #4

RIP Lotfi Aliasker Zadeh.Form an interview "Obstinacy and tenacity. Not being afraid to get embroiled in controversy. That's very much a Turkish tradition. That's part of my character, too. I can be very stubborn. That's probably been beneficial for the development of Fuzzy Logic."

[deleted]

Re: Lotfi Zadeh has died

#14

Post by pedrosorio » Sun, Sep 10, 2017, 9:54 PM UTC

dmargol1 wrote: post #11

throwaway613834 wrote: post #6

Earlier quoted context omitted.

Would you mind concisely explaining one example and application of it? I've read (for example) about possibility theory, but I hardly understand what it helps us do that probability theory didn't.

Both are ways of dealing with uncertainty, but probability theory is more about the uncertainty around which state a variable has, while fuzzy theory is the uncertainty around the states themselves. Let's say you have are taking a shower with an automated temperature control. The current temperature is set to 28 degrees Celsius, but there is a sudden shift to 24 degrees. Probability Theory: Based on prior knowledge,…

How is this different from increasing the temperature until p(cold) = p(hot)?

Re: Lotfi Zadeh has died

#15

Post by jnordwick » Sun, Sep 10, 2017, 10:15 PM UTC

I had the pleasure of having lunch with Prof Zadeh my first year in CS right around the corner from Soda Hall. I had my book out studying and he came over and talked to me and it really made me appreciate the program. Not sure about sticks out in my head so much. I think it was just the congeniality, he made me laugh and I was stressed.

My condolences go out to his family and friends, but he made a small impact on me at least.

Re: Lotfi Zadeh has died

#16

Post by vram22 » Sun, Sep 10, 2017, 10:30 PM UTC

throwaway613834 wrote: post #6

protomyth wrote: post #2

Darnit. Fuzzy sets and logic just made sense to me in so many ways and I found his writings quite interesting. RIP.

Would you mind concisely explaining one example and application of it? I've read (for example) about possibility theory, but I hardly understand what it helps us do that probability theory didn't.

>application of it?

https://en.wikipedia.org/wiki/Fuzzy_logic#Early_applications

Re: Lotfi Zadeh has died

#17

Post by mercurystills » Mon, Sep 11, 2017, 12:13 AM UTC

RIP Professor Zadeh. His work inspires aspects of my graduate research in logic.

Re: Lotfi Zadeh has died

#18

Post by imgabe » Mon, Sep 11, 2017, 1:22 AM UTC

When I first was going to college I was going to major in International Affairs. The summer before my freshman year, I read a book about fuzzy logic. (this book - https://www.amazon.com/Fuzzy-Logic-Revolutionary-Computer-Te... to be exact) and it so captivated me that I changed my major to electrical engineering. RIP Lofti Zadeh, you had a major impact on the course of my life, however indirectly.

Re: Lotfi Zadeh has died

#19

Post by dmargol1 » Mon, Sep 11, 2017, 1:27 AM UTC

pedrosorio wrote: post #14

dmargol1 wrote: post #11

Earlier quoted context omitted.

Both are ways of dealing with uncertainty, but probability theory is more about the uncertainty around which state a variable has, while fuzzy theory is the uncertainty around the states themselves. Let's say you have are taking a shower with an automated temperature control. The current temperature is set to 28 degrees Celsius, but there is a sudden shift to 24 degrees. Probability Theory: Based on prior knowledge,…

How is this different from increasing the temperature until p(cold) = p(hot)?

Since they belong to the same probability distribution, the states are not independently defined. A change that increases the probability of hot MUST decrease the probability of cold, since the probability of all states must sum to 100%.

For example, you can't have a temperature that is 80% hot AND 80% cold. This problem becomes even more apparent as you increase the number of states (lukewarm, warmish, very warm), as each state reduces the probability of another state.

The differences become more profound as you do more complicated set operations, fuzzy relations, fuzzy systems, and such. In fact, there is even fuzzy probability theory, in which you have a probability distribution of different fuzzy sets.

Re: Lotfi Zadeh has died

#20

Post by protomyth » Mon, Sep 11, 2017, 1:34 AM UTC

miobrien wrote: post #3

protomyth wrote: post #2

Darnit. Fuzzy sets and logic just made sense to me in so many ways and I found his writings quite interesting. RIP.

Any recommendations as far as his writings go? Pretty substantial list here: https://people.eecs.berkeley.edu/~zadeh/papers/index.htm

I was introduced to fuzzy logic by Earl Cox’s book[1] then I read through his papers[2]. I think reading the book helped a lot since it gave practical examples and code.

1) https://www.amazon.com/Fuzzy-Systems-Handbook-Second-Practit... I had the 1st but 2nd is better

2) that list looks pretty complete but it has been some years