MATLAB: How to add 0 values before and after a sine wave

sine wave zero values

Hi,

I have created a sine wave as follow:

Fs=2000;
t=0:1/Fs:1-1/Fs
f0=100;
y=sin(2*pi*f0*t)

Now, I would like to add 10 points with their value = 0 just before and after this sine wave. How could I do that ?

Thanks in advance!

Best Answer

It's not exactly clear what you're asking for but here are two solutions.

If you just want to add 10 points to the beginning and end of your entire signal

% number of elements to insert

nAdded = 10; 
% value to use as filler

filler = 0; 
% insert the values
fillVec = repmat(filler, 1, nAdded); 
expandedY = [fillVec, y, fillVec];     %Here's your new vector

If you want to add 10 points between each cycle of the sine curve including the beginning and end

% number of elements to insert
nAdded = 10; 
% value to use as filler
filler = 0; 
% lenght of 1 period (number of indices)
pdLength = length(y)/f0;
% insertion indices
origIdx = pdLength : pdLength : length(y);                         	%indices of y                         
expandedIdx = origIdx + cumsum(repmat(nAdded,1,length(origIdx)));   %indices of expanded y 
origIdx = [0, origIdx];                                                                         
expandedIdx = [0, expandedIdx]; 
% create new vector
expandedY = repmat(filler, 1, length(y) + f0*nAdded+nAdded);        %expanded y value
for i = 1 : length(expandedIdx)-1
    expandedY(expandedIdx(i)+nAdded+1 : expandedIdx(i+1)) = y(origIdx(i)+1 : origIdx(i+1)); 
end

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MATLAB: Sine wave oscilating around sine wave

Hi Artur,

I understand that you want to plot a sine wave and add another sine wave of smaller amplitude to it, so that it looks like noise.

The following code may be helpful:


t = 0:0.01:2;  % time

n_t = length(t);
fs = 1;  % frequency of signal

signal = sin(2.*pi.*fs.*t);
fn = 10; % frequency of noise

noise_Amplitude = 0.1;
sine_noise = noise_Amplitude.*sin(2.*pi.*fn.*t);
plot(t, signal+sine_noise)

If the requirement is to have the original signal and noisy signal in the same plot, the following code may be used:


t = 0:0.01:2;  % time
n_t = length(t);
fs = 1;  % frequency of signal
signal = sin(2.*pi.*fs.*t);
fn = 10; % frequency of noise
noise_Amplitude = 0.1;
sine_noise = noise_Amplitude.*sin(2.*pi.*fn.*t);
plot(t, signal, 'b')
hold on
plot(t, signal+sine_noise, 'r')
hold off

Regards,

Shubhankar.

MATLAB: How to create a single square wave of variable duty cycle and length.

From my assumption, you are trying to generate a square wave which looks like in the below image, when length_of_wave is 100, num_cycle is 10 and dutycycle is 0.75

In this case your code throws an error because the value of duty_cycle * length_of_wave/num_cycle is not an integer and you are trying to pass this non-integer value to "zeros" function. Hence the error.

You can make use of the following piece of code

function waveform = squareWave(length_of_wave, num_cycle, duty_cycle)
oneCycleLength =  length_of_wave/num_cycle;
t=1:oneCycleLength;
oneCycle(t)=0;
oneCycle(oneCycleLength*duty_cycle+1:end) =  1;
waveform = repmat(oneCycle, [1,num_cycle]);
plot(waveform)
end

In the above code, you have to handle the case when length_of_wave = num_cycle

Best Answer

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MATLAB: Sine wave oscilating around sine wave

MATLAB: How to create a single square wave of variable duty cycle and length.

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