eigenvalues   特征值

eigenvectors  特征向量

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an n-by-n real(实数), symmetric(对称) array

the QL method

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to sort the eigenvalues by their absolute value(绝对值) (their magnitude(量级)) rather than by their signed value(使用正负号的值).

相对概念：absolute value---signed value

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Set this keyword to return eigenvalues in ascending order (升序smallest to largest). If not set or set to zero, eigenvalues are returned in descending order (降序largest to smallest).

相对概念：ascending order---descending order

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Set this keyword to force the computation to be done in double-precision (双精度)arithmetic(计算).

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The ith row(第i行) of the returned array.

column列，row行