how do i randomly sample a sinewave?

hey can someone help me?i am trying to randomly sample sinewave but i am having no luck. i have tried Google, i tried using the help function on the 'rand' command and still i am no closer to sampling the signal.

[Azzi Abdelmalek]

What do you mean?

[Kel]

i have signal shown by the code below and would like to take random samples of the signal,

fo=4 fs=100 ts=1/fs t=0:ts:1-ts n=length(t) y=2*sin(2*pi*fo*t) plot(t,y)

Answer 1

[dpb]

yrand=y(randperm(length(y),K));

returns K random samples from y

[Kel]

thank you

Answer 2

[Image Analyst]

Try this:

fo=4
fs=100
ts=1/fs
t=0:ts:1-ts
n=length(t)
y=2*sin(2*pi*fo*t)
plot(t,y)

numberOfSamplesToTake = 20;
sampleIndexes = randperm(numel(y), numberOfSamplesToTake)
% Plot the samples;
ts = t(sampleIndexes)
ys = y(sampleIndexes)
hold on;
plot(ts, ys, 'r*');

[Kel]

thank you

[Kel]

hey i have tried your answer and matlab doesn't seem to like it. it's coming up with an error saying:

??? Error using ==> randperm Too many input arguments.

i am getting the blue sinwave but not the random red plots

[Image Analyst]

You must have a really old version of MATLAB before they added the second input argument of randperm. Try this:

numberOfSamplesToTake = 20;
sampleIndexes = randperm(numel(y))
sampleIndexes  = sampleIndexes(1:numberOfSamplesToTake)

[dpb]

Ah...good catch, IA. Never crossed my mind but my R12 doesn't include it--how quick we forget! :)

Presuming you're correct (and that's a good bet) perhaps a good use for a utility function for the OP to take the second argument.

Answer 3

[Sulaymon Eshkabilov]

An alternative solution is:

N_samples = 20;
y_rand = datasample(y, N_samples);
% OR
y_rand = randsample(y,N_samples);