see, i have this error in my code saying: ??? Attempted to access x(0); index must be a positive integer or logical. Error in ==> abc at 14 x(i)=mod(g^x(i-1), p);

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Andreea Alexandra
Andreea Alexandra 2015-7-16
评论： Walter Roberson 2015-7-16
clear all; close all; clc;
p = input('Introduceti numarul prim p= ');
g = input('Introduceti numarul prim g= ');
Nr=p-1;
x=zeros(1, Nr);
for i=1:Nr
x(i)=mod(g^x(i-1), p);
end;
disp('Rezultatul este: ');
disp(x);

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采纳的回答

Brendan Hamm
Brendan Hamm 2015-7-16
You start the loop at i=1, but then try and index x(i-1), which is the same as x(0). MATLAB starts indexes at 1 (Mathematical indexing, not programmer indexing).
That is
x = [1 2 3 4];
x(1)
ans =
1
x(0)
Subscript indices must either be real
positive integers or logicals.

更多回答（1 个）

Walter Roberson
Walter Roberson 2015-7-16
You have x(i)=mod(g^x(i-1), p); . When "i" is 1, that is mod(g^x(1-1),p) which is mod(g^x(0),p) . However there is no element #0 of a vector.
You need to think more about your initial conditions, of what is to happen on the very first iteration.

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