Merging two ranges

Question

I have a spreadsheet that has sales layed out with one year per row like this:
Sales Monthly
Year
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2012
100
125
30
90
100
174
123
251
122
135
123
345
2013
124
156
142
135
135
12
75
124
98
2014
89
196
34
Indexes
1
2
3
I would like to use the forecast function to get the forecast for the coming months and years. For example, to get the forecast for October 2013, I am using this:
=FORECAST(4,Sales Monthly :: E3:J3, Indexes :: $A$1:$C$1)
My issue comes when I try to use a similar function to get the forecast for April 2014. I'd like to join these ranges for the second argument in the forecast function:
Sales Monthly :: K3:M3
     and
Sales Monthly :: B4:D4
I've tried:
=FORECAST(4,(Sales Monthly :: K3:M3,Sales Monthly :: B4:D4) , Indexes :: $A$1:$C$1)
=FORECAST(4,(Sales Monthly :: K3:M3+Sales Monthly :: B4:D4) , Indexes :: $A$1:$C$1)
=FORECAST(4,(Sales Monthly :: K3:M3&Sales Monthly :: B4:D4) , Indexes :: $A$1:$C$1)

Answer 1

I think it would be easier to place all the data in a pair of columns (one for date and one for Sales). Add a third column which computes the forecast.
Make a second table (Maybe called "Summary") which arranges the data as shown in your original post.
I this example I placed all your data in a new column and added a forecast column.  Place you forecast formula in that column.  I made a summary table which aggregates the data the way you were viewing it before:
To confirm the formula is correct I placed a pattern in the Forecast column.  All you have to do is build the summary table as follows then update the forecast column with you formula.
In the Summary table:
B2=OFFSET(Table 12 :: $C$2, (COLUMN()-2) + 12*(ROW()-2), 0)
select B2 and fill to the right 12 columns.
select B2 thru M2 and fill down as many years as you need