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### Topic: The derivative of a volt graph (Should be easy) (Read 364 times)previous topic - next topic

#### gfvalvo

#30
##### Nov 24, 2020, 01:29 am
From what I've seen, at least 2 people posting code here have no idea what a derivative is. It's covered during the first month of CALC I. Go back and read Replies #3 and #5. Also, this: https://en.wikipedia.org/wiki/Derivative
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#### jremington

#31
##### Nov 24, 2020, 01:44 amLast Edit: Nov 24, 2020, 02:01 am by jremington
Quote
the derivative is simple the change between the last 2 values
That would be true for a derivative with respect to time, if the difference in sample times for the two measurements is exactly 1 second (assuming standard units).

But the OP has not given an understandable reason for calculating and plotting the derivative of the voltage measurements. There may be a problem of language translation.

#### gfvalvo

#32
##### Nov 24, 2020, 02:47 amLast Edit: Nov 24, 2020, 02:47 am by gfvalvo
That would be true for a derivative with respect to time, if the difference in sample times for the two measurements is exactly 1 second (assuming standard units).
Well, that would be the average rate of change over the 1 second interval. A derivative is the instantaneous rate of change as the interval approaches zero in the limit. It can only be approximated computationally. Whether or not the average rate of change over 1 second is a good approximation depends on the how quickly the value is changing and on the user's accuracy requirements, neither of which have been specified.
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#### jremington

#33
##### Nov 24, 2020, 02:52 amLast Edit: Nov 24, 2020, 02:58 am by jremington
Quote
A derivative is the instantaneous rate of change as the interval approaches zero in the limit
Yes of course, but this comment is completely irrelevant for a digital computer and discrete data. It also fails to help correct the current misunderstanding in this thread.

But the red bold highlighting is a really, really nice touch!

#### gfvalvo

#34
##### Nov 24, 2020, 03:00 amLast Edit: Nov 24, 2020, 03:05 am by gfvalvo
Yes of course, but your comment is irrelevant for a digital computer and discrete data.
You just need to read the next two sentences:
It can only be approximated computationally. Whether or not the average rate of change over 1 second is a good approximation depends on the how quickly the value is changing and on the user's accuracy requirements, neither of which have been specified.
It also fails to help correct the current misunderstanding in this thread.
You can't resolve misunderstandings until you understand what it is you want.

But the red bold highlighting is a really, really nice touch!
Emphasis mine. But, in fact, those points are key to understanding what was requested .... i.e. a derivative.
No technical questions via PM. They will be ignored. Post your questions in the forum so that all may learn.

#### jremington

#35
##### Nov 24, 2020, 03:04 amLast Edit: Nov 24, 2020, 03:04 am by jremington
Pointless argument. Bye.

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