Calculating the difference between a vector and time

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Nikolaos Zafirakis
评论： Star Strider 2019-5-5
I'm looking for a way to get this loop to work, basically I need to calculate the difference in a 3x1 vector divide by the difference in time. Does anyone have any suggestion?
t = 2000
n= 0;
for ind = 0:1:t
n= n+ind;
S(n) = (diff(x( don't know how to input the value here )))./diff(t(ind)); %x is a three element vector
end
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Nikolaos Zafirakis
Nikolaos Zafirakis 2019-5-5
So, the diff command wont work for this because if
A = [1 1 2 3]
diff(A)
= [ 0 1 1 2]
where I would need the ouput to be
=[1 0 1 1]
because
Delta_A(1) = 1 - 0 = 1 % first element - no element
Delta_A(2) = 1 - 1 = 0 % second element - first element
Delta_A(3) = 2 - 1 = 1 % third element - second element
Delta_A(4) = 3 - 2 = 1 % four element - third element
Star Strider
Star Strider 2019-5-5
If you are ‘padding’ ‘A’ with an initial 0, you need to tell MATLAB.
MATLAB does many things well, although it is sadly deficient when it comes to mind-reading.
Try this:
A = [1 1 2 3];
dA = diff([0 A])
producing:
dA =
1 0 1 1
NOTE — You need to do similar ‘padding’ for your time vector.

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回答（1 个）

Omer N
Omer N 2019-5-5
Try this:
A = [1 1 2 3];
A-[0,A(1:end-1)]
ans =
1 0 1 1

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