how does [~,I]=min(abs(strain-0.02)) work ?? (strain is a vector filled with floating point decimal numbers)

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Karvelakis Anastasios-Petros 2017-1-12

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回答： Duong Hien Thuan 2019-7-21

采纳的回答： John Chilleri

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cant get a result from find command in this manner

y1=find (strain==min(abs(strain-0.02)))

but i was proposed to use the code in the question above could someone explain how it works??

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Karvelakis Anastasios-Petros 2017-1-14

As is suspected in the first place but nonetheless thank you very much for your assistance :)

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Answer 1

John Chilleri 2017-1-12

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Hello,

Regarding your original question about:

[~,I] = min(abs(strain - 0.02))

Let's talk about what you're computing in the min() function before we discuss the function itself.

First, your vector strain has .02 subtracted from every element individually, then the absolute value of each element is taken. I'm guessing you already new this was going on, but just in case.

With respect to the min function, if you request two outputs, as you are above, min will return the minimum value and the index of that value. Let's say, for example, that abs(strain - .02) has a minimum value of .1 located in element 7 of your vector.

The min function would then return [.1, 7]. When you use the tilde (~), you are telling Matlab to not return this output; however, you are storing the index of the minimum in I.

_______________________________________________________

TLDR; I is the index of the minimum value in vector abs(strain - .02).

The documentation for min might prove useful if you're still confused.

Hope this helps!

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Answer 2

Duong Hien Thuan 2019-7-21

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Dear Sir,

I would Matlab 7.8.0 (2009A) when I use this systax it is error "Expression or statement is incorrect--possibly

unbalanced (, {, or [.". So how can I fix this problem?

Thank you!

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Steven Lord 2019-7-21

The ability to use the tilde (~) to ignore output arguments of a function call was introduced in release R2009b. Replace the tilde with a "dummy" variable name that indicates to you and to others reading your code that this output argument is not used.

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