Subscript - Symbolic serie

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Gennaro Arguzzi
Gennaro Arguzzi 2017-8-18
评论： Walter Roberson 2017-8-18
Hello everyone. Is it possible to create a symbolic serie like this: a_0, a_1, a_2, a_3? I tried with the following wrong code:
close all
clear all
syms a n
x=symsum(a_{n},n,0,3)
Thank you very much.

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Walter Roberson
Walter Roberson 2017-8-18
编辑：Walter Roberson 2017-8-18
a = [sym('a_0'), sym('a_%d', [1, 3])];
However, it is not possible to use a symbolic variable to index anything; in particular, the symbolic index, n, in symsum() cannot be used to index anything. You need to construct the individual terms and add them up, such as
x = sum( a .^ (1:4) )
  2 个评论
Gennaro Arguzzi
Gennaro Arguzzi 2017-8-18
Hi @Walter Roberson. The result is x=a_1^2 + a_2^3 + a_3^4 + a_0, instead of x=a_0+a_1+a_2+a_3. How can I get it? Thank you.
Walter Roberson
Walter Roberson 2017-8-18
I was giving an example of how to create terms based upon the individual entries and then sum those terms. For your particular case, just
x = sum(a);

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