getting right t-value for sin wave

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gedaa
gedaa 2011-3-4
hey everyone, i have this problem that involves one part, i know how to do the problem just alittle confused about this part and hope you guys can help me out,
Generate a sine wave
y(t)=sin(2*pi*f*t+7*a)
and the problem asks to generate random value for a by using randn
this is what i got but cannot seem to get the right (t) to get the sin wave, how do i determine that?
t=??
f=10;
a=randn(1,length(t));
y=sin(2*pi*f*t+(7*a));
plot(t,y)thnx alot
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gedaa
gedaa 2011-3-4
when i try different ranges for t, the wave doesn't look like a sin wave, it looks very distorted, like for example:
t=0:0.001:0.5;
Walter Roberson
Walter Roberson 2011-3-4
The upper bound on your t should be an integer if you want a whole number of periods.

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回答（1 个）

Paulo Silva
Paulo Silva 2011-3-4
ok now I got it, if the objective is to add noise to a sine wave you are doing it the wrong way.
t=0:0.001:2
f=10;
a=randn(1,length(t));
y=a/10+sin(2*pi*f*t);
plot(t,y)
if the objective is to select a random phase than
t=0:0.001:2
f=10;
a=randn*2*pi; %something ?!
y=sin(2*pi*f*t+7*a);
plot(t,y)
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gedaa
gedaa 2011-3-4
i think the 2nd part you have makes sense, what i meant by 7*a is that it's part of the problem, i cannot take it out
gedaa
gedaa 2011-3-4
the objective to the problem is actually both, first find randn for a, and then generating noise and then adding it to the sin wav

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