How can I calculate the moving average and filtering

Hi Everybody,

Yes this is my home work, need some help on it, please!

I have tried to use filter, but I got an error on it.

% calculate 2 sample running average? Is it where need to H(z) = Y(z)/X(z) ? How can I do it with this code?

x = impulse and x = zeros, how? Why?

This is so comfusing...

The input x(n0 is an impulse, and the out y(n) is the impulse response.

Adapt the program to implement a filter of the form

y(n)=0.5 x(n) + 0.5 y(n-1)

Try increasing the delay to say 100 or more e.g. (samplesCounter-100) and

listening to the impulse response by uncommenting the line at the end

soundsc(y,8000). You will need to increase the start sample by one more than

the delay, in this case 101:

for samplesCounter=101:signalEnd-signalStart
	signalStart = -2000;
	signalEnd = 2000;
	impulse_Position = 0;
	samples = (signalStart:signalEnd);
	
	x = (samples==impulse_Position);
	y = zeros(1,signalEnd-signalStart+1); %initialise output y(n) as zeros
	% x = zeros(1,20);
	% initialise input x(n) as zeros
	% x(1,2)=1; %Set x as an impulse delayed by one sample
	
	for samplesCounter = 2:signalEnd-signalStart % start at n=2 because we are using n-1 as the index below
		% y(samplesCounter)=0.5*x(samplesCounter)+0.5*x(samplesCounter-1); % calculate 2 sample running average
		y(samplesCounter)=0.5*x(samplesCounter)+0.5*y(samplesCounter-1);
	end
	
	subplot(2,1,1);
	stem(samples,x);
	ylabel('Input x(n)');
	xlabel('Sample number');
	subplot(2,1,2);
	stem(samples,y);
	grid;
	xlabel('Sample number');
	ylabel('Output y(n)');
	grid on;
	
	
	%soundsc(y,8000);

Answer 1

[Image Analyst]

You need to make a list of all the starting positions to reflect the fact that you're going to move along by samplesCounter, not by 1 which your for loop is doing now (if that's what they want - it's a bit hard to tell). Here's a hint:

y = rand(1, 5000);
samplesCounter = 100; % whatever...
indexes = 1 : samplesCounter : length(y);
for k = 2 : length(indexes)
	index1 = indexes(k-1);
	index2 = indexes(k) - 1;
	% Option 1 : Everything in between, inclusive.
	theSum1 = mean(y(index1:index2)); 
	% Option 2 : Sum y only at those two indexes, and not everything in between.
	theSum2 = 0.5 * y(index1) + 0.5 * y(index2);
	fprintf('Analyzing singnal between index %d and %d.  theSum1 = %.2f.  theSum2 = %.2f\n', ...
		index1, index2, theSum1, theSum2);
end

[Eszter Nitsch]

Thank you so much. I don't really understand this, but hey that's uni life :D :D :D

[Eszter Nitsch]

how could you listen this? Is it not the point on this question?

[Image Analyst]

I'm not sure you transcribed the problem correctly, like

Try increasing the delay to say 100 or more e.g. (samplesCounter-100)

For example why is there a minus sign there? Should it really be

Try increasing the delay to say 100 or more e.g. (samplesCounter = 100)

And when it says to increase the delay to 100 does it mean 2, then 3, then 4, then 5 and all possibilities? Or just 2 and then 100? If it's just 2 and 100, then why did it put samplesCounter in a for loop, like

for samplesCounter=101:signalEnd-signalStart

Please try to give us the exact wording so we can correct your loops and coding.

[Eszter Nitsch]

Like I said, this is my home work. I got this question as it is. I have posted this because I didn't understand it, but it's seems like the problem is not with me. I can't aswer your question because I don't know.

I have spend days on this, but still couldn't figure it out. Read a lots on matlab, how to do the for loop and also the soundsc function, but couldn't find anything useful.

I hope that with your experties could tell me what to do with this.

Thanks Anyway