翻译 1.for vectors,mean(x) return the mean value 2.for matrices,mean(x) is a row vector

For vectors, MEAN(X) is the mean value of the elements in X. For
matrices, MEAN(X) is a row vector containing the mean value of
each column.
对于向量来说,MEAN(X)是x中元素的平均值.对于矩阵来说,MEAN(X)是包含了每列平均值的行向量.