Using symSum with arrays

25 Ansichten (letzte 30 Tage)
António Santos
António Santos am 19 Dez. 2020
Kommentiert: Rui am 1 Nov. 2021
I'm currently working on a school project where i need to use fminunc to solve the following problem:
We have access to the values needed to write the function stored in arrays:
However to write the sum we need to use the elements of the arrays, something that symSum isn't letting us do.
We tried:
f = 0.5 * symsum((exp(-x*1i)-m(1i))^2,1i,1,10);
Is there any other way to represent the equation in matlab or am i missing something?
Thanks!

Antworten (2)

Rishabh Mishra
Rishabh Mishra am 24 Dez. 2020
Hi,
As per my understanding, The cause of error could be the variable ‘i’ that is being used as symbolic variable, it is used to represent complex numbers in MATLAB. Instead try using some other symbolic variable like ‘k’ or ‘l’.
You can also use the code below to store the series in variable ‘f’.
syms x
f = 0;
for k = 1:10
f = f + 0.5*(exp(-x*k) - m(k))^2;
end
Hope this Helps!

Walter Roberson
Walter Roberson am 24 Dez. 2020
You can never use a symbolic variable to index anything in MATLAB... no matter what the name of the variable is.
You have to form the definite entities and them sum() them.
m = sort(rand(1, 10),'descend'); %sample data
syms r
t = 1 : length(m);
E = sum((exp(-r*t) - m).^2)
E = 
simplify(expand(E))
ans = 
  12 Kommentare
Walter Roberson
Walter Roberson am 31 Okt. 2021
n = 5;
syms f(t)
condn1 = subs(diff(f(t), t, n-1),t,0) == 1;
cond1 = arrayfun(@(K) subs(diff(f(t),t,K),t,0) == 0, 0:n-2);
cond = [cond1, condn1]
cond = 
Rui
Rui am 1 Nov. 2021
Thankyou so much for your time Mr Roberson! I sincerely appreciate your help!
and yes, i ran the whole code successfully(this is my first time using matlab and i'm yet to learn a lot)
thanks again!

Melden Sie sich an, um zu kommentieren.

Produkte


Version

R2020b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by