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Comprehend the result of derivative with matrices operations?

Baorong Yang
Posted 10 years ago

Hi, all. I would like to compute the derivative like this: enter image description here

and I get the following result:

enter image description here

I am wondering why there is Abs and also Abs' in the answer? What does it mean by giving the two kinds of form of absolute value? Thank you.

Monica
POSTED BY: Baorong Yang
4 Replies
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POSTED BY: Gianluca Gorni
Baorong Yang
Baorong Yang
Posted 10 years ago

Thank you, Glanluca. I will check it out with your suggestion.
POSTED BY: Baorong Yang
Bill Simpson
Bill Simpson
Posted 10 years ago

Look at the FullForm of your expression before you try to take the derivative and think about what taking the derivative of each component of that might be.

I suspect that Norm is the source of some of your problems.

Abs' is the derivative of Abs and cannot be simplified further by Mathematica unless you can provide sufficient assumptions that Mathematica can determine the argument will always be positive or will always be negative.
POSTED BY: Bill Simpson
Baorong Yang
Baorong Yang
Posted 10 years ago

Thank you, Bill. I got what you mean. Actually I did't know what Abs' mean until I read your answer. I will figure out what to be fixed for my problem.

POSTED BY: Baorong Yang
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