how can I store values generated from a nested loop into an arrray ?
显示 更早的评论
if I have this code :-
function S = triangle_wave(n)
S = zeros(1,1001); %preallocation
e = [];
for t = 0:((4*pi)/1000):(4*pi)
for k = 0:n
sigma = (((-1)^k)*sin((2*k+1)*t))/((2*k+1))^2;
e(1, *???*) = sigma; *(%what should I put here instead of (???)?)*
end
r = sum(e(:));
S(1, *???*) = r; *(%what should I put here instead of (???)?)*
end
end
I can't depend on the loop's variable because they are kinda of rational numbers, so how should i store ?
采纳的回答
Andrei Bobrov
2016-8-28
编辑：Andrei Bobrov
2016-8-28
function S = triangle_wave(n)
t = linspace(0,4*pi,1001)';
k = 0:n;
S = sum(bsxfun(@times,sin(bsxfun(@times,t,(2*k+1))),(-1).^k./(2*k+1).^2),2);
end
or with for..end loop
function S = triangle_wave(n)
S = zeros(1001,1); %preallocation
t = linspace(0,4*pi,1001);%0:((4*pi)/1000):(4*pi);
k = 0:n;
for jj = 1:1001
S(jj) = sum(((-1).^k).*sin((2*k+1)*t(jj))./(2*k+1).^2);
end
end
更多回答（2 个）
Create independent index variables and increment them each pass thru the loop...
"The Matlab way" would be to use the vectorization features in Matlab syntax (see the "dot" operators .* and .^ and friends...)
BTW, if you have Signal Processing Toolbox there are a couple of waveform generation functions there; specifically sawtooth does symmetric triangle-wave form. Unless, of course, the "feature" of the rounded form of the lower number of series in the approximation is an intended result.
Thorsten
2016-8-29
The general scheme is to do define a vector of values
t = linspace(tmin, tmax, Nvalues);
and run a loop
for i=1:numel(t)
res(i) = your formula depending on t(i)
end
Of course it is often mor efficient to use vectorisation, as shown in Andrei's answer.
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