How can i find the derivative of a vector?
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I have a vector 1x80. If i put x(1,80) and y (the values of the vector from 1 to 80), i have a plot. I do not know the function which describes the plot. I want to plot the derivatives of the unknown fuction.
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You can do that approximately.
% this is the "finite difference" derivative. Note it is one element shorter than y and x
yd = diff(y)./diff(x);
% this is to assign yd an abscissa midway between two subsequent x
xd = (x(2:end)+x(1:(end-1)))/2;
% this should be a rough plot of your derivative
plot(xd,yd)
Of course the reliability of the above procedure depends on the thickness of your grid x as well as on the properties of y.
You could perhaps do a slightly (cosmetically) better job by interpolating your data using interp1.
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