How to use indexing format inside symsum function

Question

SUMIT 2023-7-1

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回答： Walter Roberson 2023-7-1

clc;

close all;

clear all;

N=2;alpha=0.5

t=zeros(1,N)

l=1:N;

t(l)=solve(chebyshevT(N,2*x-1),x);

syms m

L=symsum(t(m),m,1,2)

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SUMIT 2023-7-1

After running the program i got

''Invalid indexing or function definition. When defining a function, ensure that the arguments are symbolic variables and the body of the function is a SYM expression. When indexing, the

input must be numeric, logical, or ':'.''

please help me out

Paul 2023-7-1

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Hi Sumit,

The code results in a different error because x is not defined. Is x supposed to be symbolic variable? What is the function chebyshev? It might be helpful if to explain what the code is trying to accomplish.

N=2;alpha=0.5;
t=zeros(1,N);
l=1:N;
t(l)=solve(chebyshevT(N,2*x-1),x);
Unrecognized function or variable 'x'.
syms m
L=symsum(t(m),m,1,2)

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Answer 1

Steven Lord 2023-7-1

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在 MATLAB Online 中打开

If you want to sum the elements of a symbolic array, just use sum.

syms x

f = x.^(0:5)

f =

s = sum(f)

s =

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Answer 2

Walter Roberson 2023-7-1

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It is never possible to index by a symbolic variable at the MATLAB level. (There are some cases in the internal symbolic computing engine where indexing by a symbolic variable is possible.)