Matlab:信号处理中矩阵的正确对半

我正在从事信号处理Matlab项目。我正在执行FFT并将矩阵切成两半,以仅获得单侧频谱。我使用了以下几行代码,得到了错误“警告:冒号运算符用作索引时需要整数操作数 ":

amp = abs(y).^2/n;    % amplitude of the DFT
amp = amp(1:end/2);

为了消除警告,我尝试手动将其舍入,但当我这样做时,我得到了错误“error using round 输入参数不足。"

amp = abs(y).^2/n;    % amplitude of the DFT
amp = amp(1:round(end/2));

我想知道的是,对于单面光谱,将矩阵一分为二的正确方法是什么?作为旁注,这是整个代码:

clear all;

% Read Audio
fs = 44100;         % sample frequency (Hz)
full = audioread('song.wav');

% Remove leading 0's and select range
for i = 1:fs
    if full(i) ~= 0
        crop = i;
        break
    end
end
full = full(crop:end);

startTime = 1;
endTime = 5;

% Play song
tic
initialTime = toc;
player = audioplayer(full(fs*startTime:fs*endTime), fs);
player.play();

% Perform fft and get frequencies (hopefully in realish time with audio)
windowSize = fs/16;
for i = windowSize/2+1+fs*(startTime-1) : fs/32 : fs*endTime
    beginningChunk = round(i-windowSize/2);
    endChunk = round(i+windowSize/2);

    x = full(beginningChunk:endChunk);
    y = fft(x);
    n = length(x);     % number of samples in chunk
    amp = abs(y).^2/n;    % amplitude of the DFT
    amp = amp(1:round(end/2));
    f = (0:n-1)*(fs/n);     % frequency range
    f = f(1:round(end/2));
    while initialTime+i/fs > toc
        pause(.0001);
    end
    figure(1);
    plot(f,amp);
    axis([0 10000 0 5]);
    xlabel('Frequency');
    ylabel('amplitude');
end