Can't get user INPUT function to work!!!

I've written a quick function for a class I'm taking that removes frequencies below a specified value from an input .wav file. The function works great, but I wanted to add the ability for the user to listen to the new .wav file at the end of the function. To do this, I was trying to use the "input" function to prompt the user. My script is as follows:

function low_pass_filter(wavfile,limit,filename)

if nargin==2
    filename=('low_pass_output.wav');
end

if isstr(wavfile) && isstr(filename)

[input,FS,NBITS]=wavread(wavfile);

else
    error('Inputs wavfile and name must be strings')

end

%Perfom fast fourier tranform
ft=fft(input);

L=length(ft);

% Split transform in half
ft_cut=ft(1:L/2+1);

ft_new=zeros(L,1);

%Find and remove frequencies less than limit
freq_vec = [1/7:1/7:22050];

ind_lf = find(freq_vec < limit);

ft_cut(ind_lf(2:end))=0;

% Reconstruct fourier transform
ft_new(1:L/2+1)=ft_cut;

x = [length(ft_cut) : -1 : 2]';

ft_new((L/2)+1:L)=conj(ft_cut(x));

% Inverse fourier transform
wavfile_new=ifft(ft_new);

% Write new .wav file
wavwrite(wavfile_new,FS,NBITS,filename)

prompt='Would you like to play the edited .wav file?'
reply = input(prompt,'s')

if reply=='Y'
    sound(wavfile_new,FS)
end

The part at the end was my attempt to play the file. Just tacking on sound(wavefile_new,FS) at the end of the function will play the file, but using the "input" function as above returns this error:

??? Index exceeds matrix dimensions.

Error in ==> risk_low_pass_filter at 60
reply = input(prompt,'s')

Answer 1

[Sean de Wolski]

You overwrite the function input with the variable input as the output from your call to wavread on line 6. Thus it sees input as a variable and it's trying to index it with prompt and 's'.

Answer 2

[Neil]

How could I be so blind! Thank you!