Strange behavior of diff()

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Paul 2016-2-25

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回答： Paul 2018-3-14

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Hi all,

I'm using 2012b and I'm trying to find the difference between successive elements of a vector of uint64 numbers. Here's some of them, but I get very puzzling results form diff(). For instance:

a =       [4648759972
           4648759972
           4651621722
           4652352784
           4652733003
           4653926753]

Then diff(a) gives the wrong result:

However diff(a(1:2)) gives the correct result: 0. Also diff(a(2:3)) gives the correct result: 2861750

I've been searching for an explanation but I did not find a similar problem ever reported, and I don't understand what is happening. Can anybody explain to me what is going on here?

Thanks a lot!

Paul

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Walter Roberson 2016-2-27

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And to ask more directly,

which diff(uint64(0))

that will ensure you get the correct function shown for whatever uint64 is resolving to for you.

Paul 2018-3-14

Thanks Walter; an external toolbox rerouted the call to an external diff function with bad behavior. Deleting that function solved all problems. Sorry for the late reply.

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