better method for evaluating matrix
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JaeSung Choi
am 21 Nov. 2017
Bearbeitet: Stephen23
am 21 Nov. 2017
For given vector such as following, I want to make square matrix s such that
%constant, original form
N = 500;
x = 2*pi*linspace(0,1,N);
for i = 1:N
for j = 1:N
s(i,j) = sin(x(i)-x(j))
end
end
But it was too slow, so recently I edited it to following, but it's still too slow!!
Can anybody please help me??
%constant
N = 500;
x = 2*pi*linspace(0,1,N);
for i = 1: N;
s(:,i) = x-x(i);
end
s=sin(s);
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Stephen23
am 21 Nov. 2017
Bearbeitet: Stephen23
am 21 Nov. 2017
You really need to learn how to write vectorized code. Solving every task using lots of ugly loops is not an efficient way to write MATLAB code. Try this:
N = 500;
vec = 2*pi*linspace(0,1,N);
mat = sin(bsxfun(@minus,vec(:),vec))
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Weitere Antworten (1)
Andrei Bobrov
am 21 Nov. 2017
Bearbeitet: Andrei Bobrov
am 21 Nov. 2017
N = 500;
x = 2*pi*linspace(0,1,N);
s = sin(x(:)' - x(:));
for old versions of MATLAB:
s = sin( bsxfun(@minus, x(:)',x(:)) );
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