%this file remove noise from signal using filter
%%simulate noisy signal
Fs = 500;
f = 20;
n = [1/Fs:1/Fs:1];
x = sin(2*pi*f*n);
%add noise to the signal
y = x + rand(1,length(x));
%plot the noisy signal
subplot(3,4,1);plot(n,y);
title('noisy signal');
xlabel('time(s)');
ylabel('amplitude');
%spectral analysis of the signal
L = length(y);
NFFT = 2^nextpow2(L);
y_fft = abs(fft(y,NFFT));
%creating frequency axis
freq = Fs/2*linspace(0,1,NFFT/2+1);
%plot sigle sided amplitude spectrum
subplot(3,4,2);
plot(freq,y_fft(1:NFFT/2+1));
title('single-sided amplitude spectum of y(t)');
xlabel('frequency(Hz)');
ylabel('|y(f)|');
%%design filter and apply on the sequence.
o = 5;
wn = [3 7]*2/Fs;
[b,a] = butter(o,wn,'bandpass');
%see frequency response of the filter
[h,w] = freqz(b,a,1024,Fs);
subplot(3,4,3);
plot(w,20*log10(abs(h)));
title('magnitude response of the filter');
xlabel('frequency(Hz)');
ylabel('magnitude');grid on;
%filter the signal
y_filt = filter(b,a,y);
subplot(3,4,4);
plot(n,y_filt);
title('filtered signal');
xlabel('time(s)');
ylabel('amplitude');
By Executing this programe the error occurs like the following.how can it will be error free and give output ,kindly suggest me.
removenoise
Error using subplot (line 109)
Attempt to call constructor handle with incorrect letter case.
Error in removenoise (line 10)
subplot(3,4,1);plot(n,y);
