Let's assume you data is in A1:B100
Let's assume that column A had real dates formatted to display as Jan-08
In D1:D12 enter dates fro the first of each month (Jan thru Dec) of current
year
Format this to display as Jan, Feb using custom format mmm
In E1 enter
=SUMPRODUCT(--(MONTH($A$1:$A$4)=MONTH(D1)),$B$1:$B$4)/SUMPRODUCT(--(MONTH($A$1:$A$4)=MONTH(D1)))
Copy down to E12
Plot the table you have just made
If the A column actually has text: Jan-08:
In D1:D12 enter the month abbreviations: Jan , Feb ,,,Dec
In E1 use
=SUMPRODUCT(--(LEFT(A$1:A$3,3)=D1),$B$1:$B$3)/SUMPRODUCT(--(LEFT($A$1:$A$3,3)=D1))
Copy down to E12
Plot chart
best wishes
--
Bernard V Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme
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