backward,forward, and central Difference
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Can any body help me understand how to do numerical differentiation? example:
t = 0:5:100; Z = cos(10*pi*t)+sin(35*pi*5);
how can I find the backward,forward and central difference at t = 99?
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Answers (4)
Jan
on 9 Nov 2011
For :
t = 0:5:100;
Z(t) = cos(10*pi*t)+sin(35*pi*5);
you cannot find the forward and central difference for t=100, because this is the last point. Central differences needs one neighboring in each direction, therefore they can be computed for interior points only. For the first point, you can get a forwrad difference, for the last point a backward difference only:
dZ1 = (Z(2) - Z(1)) / (t(2) - t(1));
dzi = (Z(i+2) - Z(i-1)) / (t(i+1) - t(i-1)); % 1 < i < 100
dZ100 = (Z(100) - Z(99)) / (t(100) - t(99));
4 Comments
Friedrich
on 9 Nov 2011
Hi,
lets say you like to get Z'(t_0) with the forward difference. You do the following
Z'(t_0) = ( Z(t_0 + h) - Z(t_0) ) / h
where h is a small offset. You actually calculate the slope of a straight line which goes through Z(t_0 + h) and Z(t_0) for forward differences.
4 Comments
Friedrich
on 10 Nov 2011
No, i would put it in the formula above (t_0 = x in that case).
So (cos(10*pi*(x+h)) + sin(35*pi*5) - .....) / h
Fahad Maqsood
on 9 Dec 2018
Hi
I am new to matlab and struggling with it. any one who can help me getting started
Given: x 1 2 3 4 5 6
f(x) 2 3 1 5 4 1
Estimate f′(4) using the forward, backward, and centered difference method with h = 1.
and second order polynomial.
3 Comments
Fahad Maqsood
on 13 Dec 2018
As i mentioned i never worked on matlab before, i searched hard for it but could not find any related problems. It has been posted for those could help others getting started. Well you have your own opinion keep it in your pocket.
Steven Lord
on 13 Dec 2018
If you show us what you've tried so far and explain the specific difficulty you're experiencing, we may be able to provide some guidance.
If you're not even sure where to start because you're new to MATLAB, I recommend working through the MATLAB Onramp tutorial available from the Tutorials section of the Support page on this website (click the Support button at the top of this page.)
If you're not sure where to start because of the subject matter of the question, I recommend contacting your professor and/or your teaching assistant and asking them for help with the material.
LE TRAN
on 14 Mar 2024
hello everyone, I have a math problem with an error in the code.Please refer to the code
- Build a code to Estimate the first derivative of the following function at x=0.5 using h=0.5, 0.25, and 0.1 for the forward, backward, and centre difference approximation schemes.
- Make an analysis and draw some conclusions based on the results obtained.
- f(x)= -0,1*x^4-0,15*x^3-0,5*x^2-0,25*x+1,2
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