sine wave plot

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aaa
aaa 2012-4-24
回答： Ranjita 2024-9-30
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?
  6 个评论
显示 4更早的评论
Walter Roberson
Walter Roberson 2021-8-10
@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
Gokul Krishna N 2021-10-13
Just been reading the comments in this question. Hats off to you, sir @Walter Roberson

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采纳的回答

Rick Rosson
Rick Rosson 2012-4-24
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
  2 个评论
Rajasekaran
Rajasekaran 2013-3-14
Thanks for your reply & detailed answer.
Nauman Hafeez
Nauman Hafeez 2018-12-28
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.

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更多回答（7 个）

Mike Mki
Mike Mki 2016-11-29
Dear Mr. Rick, Is it possible to create knit structure in Matlab as follows:
Junyoung Ahn
Junyoung Ahn 2020-6-16
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)')
  2 个评论
DARSHAN
DARSHAN 2023-1-8
why should we multiply f with 100?
Walter Roberson
Walter Roberson 2023-1-8
I think the intent was to give 100 samples per cycle.

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Robert
Robert 2017-11-28
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
shampa das
shampa das 2020-12-26
编辑：Walter Roberson 2021-1-31
Ran in:
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);
soumyendu banerjee
soumyendu banerjee 2019-11-1
%% if Fs= the frequency u want,
x = -pi:0.01:pi;
y=sin(Fs.*x);
plot(y)
sevde busra bayrak
sevde busra bayrak 2020-8-24
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')
Ranjita
Ranjita 2024-9-30
Ran in:
clc
clear all
fs = 10000;
T=1/fs
T = 1.0000e-04
f1 = 100;
f2= 50;
L= 10000;
t = (0:L-1)*T;
x1 =sin(2*pi*f1*t)+4*cos(2*pi*f2*t)
x1 = 1×10000
4.0000 4.0608 4.1174 4.1696 4.2171 4.2598 4.2973 4.3294 4.3561 4.3770 4.3920 4.4009 4.4037 4.4000 4.3898 4.3730 4.3496 4.3193 4.2821 4.2381 4.1871 4.1292 4.0643 3.9926 3.9139 3.8284 3.7362 3.6374 3.5320 3.4202
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figure
subplot(2,2,1)
plot(t,x1)
axis([0 0.1 -1 6]);
title('SS Function');
xlabel('time');
ylabel('magnitude');
%frequency domain conversion and plotting
Y_x1=fftshift(fft(x1));
subplot(2,1,2)
plot (-(fs/2-fs/L)-1:(fs/L):(fs/2-fs/L),abs(Y_x1))
axis([-700 700 0 max(abs(Y_x1))+10000]);
title('Magnitude spectrum of S1 Function');
xlabel('Frequency(Hz)');
ylabel('magnitude');
sgtitle('Frequency Domain Representation of S1 Function');

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