matlab-生成正弦波

function output = gen_sin( fs, fs1, time)
% 生成正弦波
% fs ：系统采样率（Hz）
% fs1：数据频率（Hz）
% time;时间(ms)
t=0:2*pi/(fs/fs1):2*pi;
temp = sin(t);
ampl = NaN;
len = length(temp)-1;
j = 1;
    for i=1:1:round(time*fs/1000)
        if ( j > len )
            j = 1;
        end
        ampl(i) = temp(j);
        j = j + 1;
        end
 output = ampl;
end

clear all;
close all;
fs = 1000;
fs1= 5;
times = 2000;
y = gen_sin(fs, fs1, times);
figure(1);
plot(y);

ampl = abs(fft(y)/length(y));
f = 0:fs/length(ampl):fs;
f = f(1:length(ampl));
figure(2);
plot(f, ampl);