79 lines
1.4 KiB
Matlab
79 lines
1.4 KiB
Matlab
Y = [] %it doesn't like when I don't add this
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% ze basic functions for differentiating
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function y = f_newt_diff1(Y,h)
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y = ( Y(2) - Y(1) ) / h
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end
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function y = c_newt_diff1(Y,h)
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y = ( Y(2) - Y(1) ) / ( 2 * h )
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end
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function y = b_newt_diff1(Y,h)
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y = ( Y(1) - Y(2) ) / h
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end
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% this one retrieves elements from "table" and decides which one to usejava
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% uses Centered when possible
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function y = newt_diff_fr1(Y,X,x,h)
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idx = find(X==x);
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if (idx == length(X)) %backwards
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elems = [Y(idx), Y(idx-1)]
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y = b_newt_diff1(elems,h)
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elseif (idx == 1) %forwards
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elems = [Y(idx), Y(idx+1)]
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y = f_newt_diff1(elems,h)
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else %centered
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elems = [Y(idx-1), Y(idx+1)]
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y = c_newt_diff1(elems,h)
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endif
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endfunction
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X = [0 1 2 3 4]
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Y = X.^2
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newt_diff_fr1(Y,X,1,1)
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% functions but...level 2!
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function y = f_newt_diff2(Y,h)
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y = ( Y(3) - 2 * Y(2) + Y(1) ) / h^2
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end
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function y = c_newt_diff2(Y,h)
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y = ( Y(3) - (2 * Y(2)) + Y(1) ) / h^2
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end
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function y = b_newt_diff2(Y,h)
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y = ( Y(1) - 2 * Y(2) + Y(3) ) / h^2
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end
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%Defaults to center level 2
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function y = newt_diff_fr2(Y,X,x,h) %Y -> f(x), X -> x, x -> value we want, h..
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idx = find(X==x);
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if (idx == length(X)) %forwards
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elems = [Y(idx), Y(idx-1), Y(idx-2)]
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y = b_newt_diff2(elems,h)
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elseif (idx == 1) %backwards
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elems = [Y(idx), Y(idx+1), Y(idx+2)]
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y = f_newt_diff2(elems,h)
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else % centered
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elems = [Y(idx-1), Y(idx), Y(idx+1)]
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y = c_newt_diff2(elems,h)
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endif
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endfunction
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