HARMEAN function
Description
Harmonic mean function. HARMEAN(range) computes the harmonic mean of the contents of the cells in the specified range.
The argument range can be a list of numbers, cell addresses, cell ranges (such as A1:A10).
Range can also be a matrix. In that case the function returns a matrix with one row and the same number of columns, with each element the HARMEAN of the corresponding column. If range is a row matrix, it is converted to a column matrix first.
The harmonic mean is calculated as follows:
$$\frac{n}{\frac1{x_1} + \frac1{x_2} + \cdots + \frac1{x_n}} = \frac{n}{\sum\limits_{i=1}^n \frac1{x_i}} $$
The harmonic mean is undefined for a data set that contains zero or negative values.
$$\frac{n}{\frac1{x_1} + \frac1{x_2} + \cdots + \frac1{x_n}} = \frac{n}{\sum\limits_{i=1}^n \frac1{x_i}} $$