目前的代码是一个matlab函数，它提供给定信号x[n]的短时傅立叶变换（stft）。该函数是matlab命令“光谱图”的一个替代项。功能输出为：

1）一个具有复杂stft系数的矩阵，该矩阵具有跨列时间和跨行频率；

2）频率矢量；

3）时间矢量。
为了阐明函数的用法，给出了一个示例。为了方便起见，输入和输出参数在函数的开头给出。(The present code is a Matlab function that provides a Short-Time Fourier Transform (STFT) of a given signal x[n]. The function is an alternative of the Matlab command spectrogram The output of the function is
1) a matrix with the complex STFT coefficients with time across the columns and frequency across the rows;
2) a frequency vector;
3) a time vector.

An example is given in order to clarify the usage of the function. For convenience, the input and output arguments are given in the beginning of the function.)