sine wave plot

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?

[Ahmed Grera]

How many cycles do you need in drawing?

[Govinda Nahak]

in sine function in MATLAB it is always sin(wt). here frequency w is in radian/sec not f (in HZ) so w will give you the no.of the cycle.

suppose w=1 it is one cycle and so on

if you want to use the sin(2*pi*60*t) you can use the sind(2*pi*9.545*t). why i use the 9.545 bcz we should convert the f to w in the time interval of 2*pi.

[Jorge Ignacio Cisneros Saldana]

How can we make it 3 phase system? for 50 Hz and 230 V peak to peak

[Mellamputi Sai geetha]

x(t)=∆(t+7)-∆(t-7) prepare a MATLAB graph

[SREEGANESH VAKA]

Write a MATHLAB code to generate a CT step signal with peak Amplitude of 5 Volts and should be plotted on the time scale from 0 to 1000.

[Walter Roberson]

That does not seem to be relevant to the Question that was asked?

[Subhranil Barman]

Write a MATHLAB code to generate a CT step signal with peak Amplitude of 5 Volts and should be plotted on the time scale from 0 to 1000.

[Muqtadir Rahman]

• Generate a cos wave for 2 cycle
• Show only a full cycle in figure.
• Write meaningful x & y label
• Write your name in Title

[Walter Roberson]

@Muqtadir Rahman that does not appear to be a solution to the question the user asked in 2012 ??

[payal soni]

how to write ∑ 𝑐𝑜𝑠𝑡𝑗,1 𝑇 𝑖∈𝐺 𝑝𝑖 = 0.105 ∗ ∑𝑖∈𝐺 𝑝𝑖,𝑗 in matlab

[Walter Roberson]

payal soni

please start a new question for that, and show an image of the equation. You will a probably also need to talk more about what G is.

[Arif Raihan]

Sample a continuous time cosine signal of amplitude 3 V. Sir please solve this.

[Walter Roberson]

@Arif Raihan

In order to solve that, you need some hardware to do analog to digital conversion between your 3V source and MATLAB.

3V is too large for audio work, so you are not going to be able to use microphone inputs to do this. You are going to need hardware such as a National Instruments ADC or at least an arduino (you might need to put in a resistor to lower the voltage range.)

The software programming needed on the MATLAB end depends a lot on which analog to digital convertor you use.

The appropriate analog to digital convertor to use is going to depend in part on what sampling frequency you need to use; you did not define that, so we cannot make any hardware recommendations yet.

[Gokul Krishna N]

Just been reading the comments in this question. Hats off to you, sir @Walter Roberson

Answer 1

[Rick Rosson]

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

[Rajasekaran]

Thanks for your reply & detailed answer.

[Nauman Hafeez]

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]

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]

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.

[MUHAMMAD BASIM]

Can anybody please provide the MATLAB code for kalman filter for filtering out noise from a sine signal.please refer to attached picture for detail

[Walter Roberson]

When you searched MATLAB Answrs for kalman filter, and found the more than 600 results, what was unique about your situation such that none of the more than 600 results were suitable for even starting the code?

[shail bala]

sir this wave form mathwork is used for reconstruction of the signal through interpolation

[MD RAJIBUL HOSSAIN RUBEL]

There are two numbers given as -5+2i 3-2i using Plot and Stem function show the output of this equation

[Hajha]

sir can you please help me with my question?

[Walter Roberson]

@Hajha

I do not find any questions posted by you ?

Answer 2

[Mike Mki]

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

[DGM]

See this thread:

https://www.mathworks.com/matlabcentral/answers/1864158-plotting-mutually-occluding-curves-in-2d

Answer 3

[Junyoung Ahn]

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)')

[DARSHAN]

why should we multiply f with 100?

[Walter Roberson]

I think the intent was to give 100 samples per cycle.

Answer 4

[Robert]

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

Answer 5

[shampa das]

clc; t=0:0.01:1; f=1; x=sin(2*pi*f*t); figure(1); plot(t,x);

fs1=2*f; n=-1:0.1:1; y1=sin(2*pi*n*f/fs1); figure(2); stem(n,y1);

fs2=1.2*f; n=-1:0.1:1; y2=sin(2*pi*n*f/fs2); figure(3); stem(n,y2);

fs3=3*f; n=-1:0.1:1; y3=sin(2*pi*n*f/fs3); figure(4); stem(n,y3); figure (5);

subplot(2,2,1); plot(t,x); subplot(2,2,2); plot(n,y1); subplot(2,2,3); plot(n,y2); subplot(2,2,4); plot(n,y3);

Answer 6

[soumyendu banerjee]

%% if Fs= the frequency u want,
x = -pi:0.01:pi;
y=sin(Fs.*x);
plot(y)

Answer 7

[wilfred nwakpu]

   %%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;

Answer 8

[sevde busra bayrak]

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')

Answer 9

[Ana Maria]

Implement a function to generate a column vector containing a sine wave, sin(2πf(t)t), with a growing frequency, f(t) from f(0) = f1 to f(T) = f2. The inputs of the function are the duration, T in seconds, the frequencies, f1 and f2, in Hz and the sampling rate, fs, in samples per second x = chirpT one(T, f1, f2, fs)

[Walter Roberson]

@Ana Maria

Could you explain how the process you set out will solve the original question posted in 2012 ?

[DGM]

You're copying and pasting an assignment text. This is not an answer, so it doesn't belong here as an answer. I'm compelled to keep things where they belong and remove them when they don't.

This is ultimately your task to perform. The information already present on this page is largely sufficient to complete it. I'm sure with enough effort, you can find even more specific examples elsewhere on the forum.

If you want to ask a question, please open a new question using the 'ask' button at the top of the page. If and when you do, ask an actual question, but also be prepared to prove that you've exhausted what due diligence provides.

https://www.mathworks.com/matlabcentral/answers/8626-how-do-i-get-help-on-homework-questions-on-matlab-answers

EDIT:

To prove the point, I'm just going to grab the answer directly above and make one simple change. Other than changing the specific parameters (a matter of choice), the only real change is that instead of being a scalar, freq is a vector generated from two specified values.

% these are parameters
samplerate = 500;
duration = 2;
flim = [0 8];

% both these vectors have the same size
time = 0:1/samplerate:duration;  % time is a linear vector
freq = linspace(flim(1),flim(2),numel(time)); % freq is a linear vector

Generating a vector of uniformly-spaced values is very basic MATLAB stuff. The remaining change necessary to make freq work as a vector is also basic (literally one single character), but I have to leave something for you to do.