Moving average filter problem.

I have an assignment that wants me to create a moving average filter using no filter functions coded into matlab.

gr is a waveform being run through the filter. It is a fourier approximation for a square wave 4/pi * SUM(sin((i*pi)/2)*(400*t+1) where i = {1,3,5,7,9}. gr also must have some .4*randn(size(t)) added to it.

The equation for an M point moving average filter is y(n) = 1/M * SUM from k=0 to k=M-1(x(n-k))

I'm doing something wrong with my indexing and I can't tell where :(

%Assignment 9 - Moving Average Filter
fs = 10000;
M = 8;
t = 0:1/fs:.05;

g1 = (4/pi)*sin((pi/2)*((400*t)+1))+.4*randn(size(t));
g3 = (4/pi)*(1/3)*sin((3*pi/2)*((400*t)+1))+.4*randn(size(t));
g5 = (4/pi)*(1/5)*sin((5*pi/2)*((400*t)+1))+.4*randn(size(t));
g7 = (4/pi)*(1/7)*sin((7*pi/2)*((400*t)+1))+.4*randn(size(t));
g9 = (4/pi)*(1/9)*sin((9*pi/2)*((400*t)+1))+.4*randn(size(t));

gr = g1 + g3 + g5 + g7 + g9 + .4*randn(size(t));

y = zeros(M,length(t));
for i = 1:M
    if i == 1
        y(i) = sum(gr);
    else
        y(i) = sum((4/pi)*sin((pi/2)*((400*(t-i)+1)))+ (4/pi)*(1/3)*sin((3*pi/2)*((400*(t-i)+1)))+ (4/pi)*(1/7)*sin((7*pi/2)*((400*(t-i)+1)))+ (4/pi)*(1/9)*sin((9*pi/2)*((400*(t-i))+1)))+.4*randn(size(t)));
    end
end

plot(t,y)

Answer 1

[Walter Roberson]

You have )))+.4*randn . That is one too many ) at that point, should be ))+.4*randn