I am trying to filter noise present in the signal so that it gives me a smooth curve.But the signal is not getting filtered.Any help?

Following is the code to filter out noise.Kindly let me know why i dont see the filtered signal.I want to get output like the one attached.Attached is the input file.I am working on the last column.

file = 'forRef_2.xls';

col = xlsread(file,'J:J');x_mags=abs(fft(col));

%num_bins=length(x_mags);

[b a]=butter(2,0.3,'low');

x_filtered=filter(b,a,col);

figure;

plot(col)

hold on

plot(x_filtered,'r')

[preeti visweswaran]

Can i get a help in this