How do I calculate the average slope of an array in Excel?

Question

I have a series of returns in a column of cells and would like to calculate the average slope calculated from the differences between each return value.

Returns:          
0.05              
0.06 
0.04 
0.07 
0.05 
0.06

I do not want to create a row for the differences because I have more columns of return streams beside the one above. I'm looking for a non-vba solution.

The answer I'm looking for is shown below:

Required Value: = Sum of slopes/No. of periods
Ans: -0.001666666

Cheers!

Answer 1

You can use a SUMPRODUCT() to get the sum of the differences then divide it by the count:

This one subtracts the lower from the upper:

=SUMPRODUCT($A$2:$A$6-$A$3:$A$7)/COUNT(A2:A7)

If you want it the other way around, by subtracting the upper from the lower then use this:

=SUMPRODUCT($A$3:$A$7-$A$2:$A$6)/COUNT(A2:A7)

Answer 2

At risk of being controversial:-

=(A7-A2)/COUNT(A3:A7)

because (A7-A6)+(A6-A5)...+(A3-A2) = A7-A2 and because there are only 5 differences between the 6 numbers, so my answer is 0.002..