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Hi,

I am having some trouble plotting a sine wave and i'm not sure where i am going wrong.

i have

t = [0:0.1:2*pi]

a = sin(t);

plot(t,a)

this works by itself, but i want to be able to change the frequency. When i run the same code but make the change

a = sin(2*pi*60*t)

the code returns something bad. What am i doing wrong? How can i generate a sin wave with different frequencies?

Rick Rosson
on 24 Apr 2012

Please try:

%%Time specifications:

Fs = 8000; % samples per second

dt = 1/Fs; % seconds per sample

StopTime = 0.25; % seconds

t = (0:dt:StopTime-dt)'; % seconds

%%Sine wave:

Fc = 60; % hertz

x = cos(2*pi*Fc*t);

% Plot the signal versus time:

figure;

plot(t,x);

xlabel('time (in seconds)');

title('Signal versus Time');

zoom xon;

HTH.

Rick

Nauman Hafeez
on 28 Dec 2018

How to calculate Fs for a particular frequency signal?

I am generating a stimulating signal using matlab for my impedance meter and it gives me different results on different Fs.

Sameeksha Singh
on 30 Oct 2020 at 8:19

This task has students detect the frequency of a sinusoid embedded within a noisy signal. To do so, we generate a set of candidate sinusoidal functions, each representing our guess for the unknown frequency. We then cross-correlate these functions with the input signal and then use the magnitude of the peaks in the output as a score for the presence of each frequency in the input signal. Let our signal be a sinusoid x(t) containing an unknown frequency that lies in the range from 1 Hz to 2 Hz. This signal is sampled at a rate of 30 samples per second by an analog-to-digital converter to create a digital signal x[n]. In this circumstance we will proceed as follows:

1. Hypothesize a sinusoidal sequence having frequencies ranging from f = [1Hz, 2Hz] in increments of 0.2 Hz. Create a digital lter h[n] to cross-correlate with the input x[n].

2. Adjust values of your lter coecients so that the sum of the lter coecients is equal to 0. This can be accomplished by sampling the sinusoid symmetrically about the origin since the sine function is odd symmetric, i.e., sin(x) = − sin(−x). Note that since sin(0) = 0 the sample h[0] has no contribution to either your lter or the output value.

3. For each sequence, cross-correlate your signal with the input signal. 4. Observe the output signal and nd the cross-correlation signal having largest peak response. This frequency is then the best guess for the unknown frequency in the input signal.

please help me I am new to MATLAB

Jessica
13 minutes ago

Att: Sameeksha Singh

Do not ask questions within other persons questions.

Here is how you do it:

Top right there is a "Ask the Community" button.

Click and copy/paste your question there.

Make sure that you have as much code or specific facts with, not so much text as possible.

Mike Mki
on 29 Nov 2016

Dear Mr. Rick, Is it possible to create knit structure in Matlab as follows:

Robert
on 28 Nov 2017

aaa,

What goes wrong: by multiplying time vector t by 2*pi*60 your discrete step size becomes 0.1*2*pi*60=37.6991. But you need at least two samples per cycle (2*pi) to depict your sine wave. Otherwise you'll get an alias frequency, and in you special case the alias frequency is infinity as you produce a whole multiple of 2*pi as step size, thus your plot never gets its arse off (roundabout) zero.

Using Rick's code you'll be granted enough samples per period.

Best regs

Robert

soumyendu banerjee
on 1 Nov 2019

%% if Fs= the frequency u want,

x = -pi:0.01:pi;

y=sin(Fs.*x);

plot(y)

wilfred nwakpu
on 1 Feb 2020

%%Time specifications:

Fs = 8000; % samples per second

dt = 1/Fs; % seconds per sample

StopTime = 0.25; % seconds

t = (0:dt:StopTime-dt)'; % seconds

%%Sine wave:

Fc = 60; % hertz

x = cos(2*pi*Fc*t);

% Plot the signal versus time:

figure;

plot(t,x);

xlabel('time (in seconds)');

title('Signal versus Time');

zoom xon;

Junyoung Ahn
on 16 Jun 2020

clear;

clc;

close;

f=60; %frequency [Hz]

t=(0:1/(f*100):1);

a=1; %amplitude [V]

phi=0; %phase

y=a*sin(2*pi*f*t+phi);

plot(t,y)

xlabel('time(s)')

ylabel('amplitude(V)')

sevde busra bayrak
on 24 Aug 2020

sampling_rate = 250;

time = 0:1/sampling_rate:2;

freq = 2;

%general formula : Amplitude*sin(2*pi*freq*time)

figure(1),clf

signal = sin(2*pi*time*freq);

plot(time,signal)

xlabel('time')

title('Sine Wave')

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