Smoothing a noisy data set

As a homework assignment, I need to make a function that uses a moving average to smooth a noisy data set.

The function I need to make takes a data set to be smooothed "y", the corresponding vector for the indipendent variable 't", as well as the number of data points used in the moving average "N" then return the sothed data set "ys" and a corresponidng time vecotr for the smoothed data "ts".

What I have so far:

function [ys,ts] = smoothN(y,t,N)
%smooothN.m uses a moving average to smooth data
%   Input: y: data vector to be smoothed
%   Input: t: the corresponding time vector to y
%   Input: N: specifies how many data points to use when calculating the moving average
%   Output: ys: the smoothed data vector
%   Output: ts: the coresponding time vector

for i=1:length(y)
    add=0;
    for j=i:i+(N-1) % this for loop finds the summ of the elements within the moving avergae
        add=add+y(i);
    end
    ys(i)=add/N; %finds the average and sets it into the smoothed vector
    ts(i)=t(i); % adjusts the corresponding time vector
end
%Bradley

Unortunatly, this just returns the original vector and I can't figure out why.

Please help me

Answer 1

[Astha Singh]

Hello,

The error is in variable indexing, in the second for-loop,

add = add+y(j)

instead of "add = add+y(i)".

Also, you would need to take care of the indexing of variable 'i' when the last 'N' sample values of 'ys' are being calculated.