MATLAB: Numerical derivative central difference

central differencenumerical derivative

Hello, i try to write a code about central difference. But something is wrong. My code is below. What is wrong?
function derivativecentral(numericalvalue, step, n)
    centraltable=[0 -1 0 1 0;0 1 -2 1 0;-1 2 0 -2 1;1 -4 6 -4 1];
    x=numericalvalue-2*step: step:numericalvalue+2*step;
    m=2;
    if (n/2)==floor(n/2); m=1;  coeff = centraltable(n,:);
       der=sum(coeff.*fonk(x)) / (m*step^n);
       display(der);
    end
end
function [f] = fonk(x) f=x*exp(x); end
At the end of code, i am writing derivativecentral(0,0.1,1)
But there is nothing.

Best Answer

The code displays nothing because the condition did not become true. Try the following code with a different input
derivativecentral(0,0.1,4)
function derivativecentral(numericalvalue, step, n)
    centraltable=[0 -1 0 1 0;0 1 -2 1 0;-1 2 0 -2 1;1 -4 6 -4 1];
    x=numericalvalue-2*step: step:numericalvalue+2*step;
    m=2;
    if (n/2)==floor(n/2); m=1;  coeff = centraltable(n,:);
       der=sum(coeff.*fonk(x)) / (m*step^n);
       display(der);
    end
end
function [f] = fonk(x) 
f=x.*exp(x); % <---- this is syntax for element-wise multiplication
end
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