COVARIANCE.S function in excel is a statistical function. This function is used to find the sample covariance of two data sets. For example it can be used to keep check on how to assets are moving together. This is a worksheet function and can be entered into the cell in which count is required.
Syntax:= COVARIANCE.S(array1,array2)
The COVARIANCE.S function syntax has the following arguments:
 Array1 (required argument) – This is the first array of numeric values.
 Array2 (required argument) – This is the second array of numeric values.
Example: Let’s look at some Excel COVARIANCE.S function examples and explore how to use the COVARIANCE.S function as a worksheet function in Microsoft Excel:
Suppose we are given data about the weekly returns of Stock A and percentage of change in the market index (NASDAQ):
Let’s use the function to understand if there is any covariance between the stock returns and NASDAQ returns.
Syntax: =COVARIANCE.S(B2:B20,C2:C20)
Result: 0.000684099
The result indicates that there exists a positive correlation between the two.
Note:
 The arguments must either be numbers or be names, arrays, or references that contain numbers.
 If an array or reference argument contains text, logical values, or empty cells, those values are ignored; however, cells with the value zero are included.
 If array1 and array2 have different numbers of data points, COVARIANCE.S returns the #N/A error value.

If either array1 or array2 is empty or contains only 1 data point each, COVARIANCE.S returns the #DIV/0! error value.