Try this:

=(SUMIF(A:A,O1,C:C)/COUNTIF(A:A,O1) - SUMIF(A:A,N1,C:C)/COUNTIF
(A:A,N1)) / (O1-N1)

This takes the average of all the values for each date, as requested
in your other thread.

Hope this helps.

Pete

On Jan 27, 8:08*am, beto wrote:
How can I get the slope from the following data:

I need to get the slope from ColumnC, from date 1/6/2010 to 1/8/2010.
Data I know:
from:1/6/2010 all the way to 1/8/2010.
N1=1/6/2010
O1=1/8/2010
using as "x axis" the dates and "y axis" the values in ColumnC

any Possible solution.?

ColumnA ...ColumnB ColumnC
1/5/2010 .....234......... 487
1/6/2010 .....456 .........898
1/6/2010 .....789 .........998
1/6/2010 .....123 ,........123
1/7/2010 ......345.........984
1/7/2010 ......678........ 783
1/7/2010 ......897........ 234
1/8/2010 ......098........ 543
1/8/2010 ......738........ 928
1/9/2010 ......123........ 123
1/9/2010 ......421........ 987