How do I create forecast chart for view 3 months in the future (Jan-Mar 2018)?

[panwipa2528]

If I have data sale from 2016-2017 as below, How do I create forecast chart for view 3 months in the future (Jan-Mar 2018)?

YearMonth	Sale
201601	51,430
201602	88,265
201603	80,294
201604	77,470
201605	77,790
201606	82,874
201607	79,558
201608	75,460
201609	69,899
201610	71,511
201611	87,371
201612	102,744
201701	67,424
201702	78,588
201703	90,834
201704	85,888
201705	76,152
201706	74,970
201707	82,990
201708	80,470
201709	82,600
201710	67,080
201711	82,221
201712	38,686

[Anil_Babu_Samineni]

May be this?

Left(YearMonth,4) as Year

Expression should be this?

if(Year<>'2017',sum(Sale), Linest_m(total aggr(if(sum(Sale),sum(Sale)),Year),Year)*Year+Linest_b(total aggr(if(sum(Sale),sum(Sale)),Year),Year))

[sunny_talwar]

What are the expected numbers you hope to see for the future months? Is this something you need in the script or on the front end?