Symbolic Differentiation and Then Numeric Calculation for Multiple Arrays

Question

Burak Duran 2020-6-30

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https://ww2.mathworks.cn/matlabcentral/answers/557401-symbolic-differentiation-and-then-numeric-calculation-for-multiple-arrays

编辑： darova 2020-7-1

Dear All,

I have two different arrays; F(1x4), d(1x8). d matrice is actually consisted of two sub matrices d1(1x4) and d2(1x4). I mean d=[d1;d2

My pupose is to write a symbolic function. I know that maybe the funciton should be out of a loop, but I can't understand how can I handle this.

Actually, my function is like g(F,d)=F-500*d1*d2 and then I want to take differentiation of this function according to d1 and d2. Next, give the numeric value coming from F and d arrays for i'th iteration. So, get numeric after conversion.

d is like that [d1 d2 d1 d2 d1 d2 d1 d2]

How can I express such a function symbolic, take differentiation and then put the numeric values for that loop coming from F and d matrices.

Example;

g(F,d)=F(i)-500*d(2*i-1)*d(2*i+1)
diff(g,d(2*i-1))=-500*d(2*i+1)
for i=1
g1_Numeric(1)=double(g1(F(1),d(1),d(2)))

Written code is like as follow;

    for i=1:4
        syms g(F,d1,d2)
        g(F,d)=F(i)-500*d(2*i-1)*d(2*i+1)
        g1=-((diff(g,d(2*i-1))
        g1_Numeric(i)=double(g1(F(i),d(2*i-1),d(2*i+1)))
        g2=-((diff(g,d(2*i+1))
        g2_Numeric(i)=double(g2(F(i),d(2*i-1),d(2*i+1)))
    end