Hi Alex, I appreciate your effort,thanks for your input. I seem to understand how the idm model works,and i have made a demo, but the forecast values seem to be behaving unexpectedly,the intermittent time series is : DATE QTY 1990-02-01 0 1990-03-01 0 1990-04-01 0 1990-05-01 0 1990-06-01 3 1990-07-01 0 1990-08-01 0 1990-09-01 3 1990-10-01 0 1990-11-01 0 1990-12-01 6 1991-01-01 0 1991-02-01 7 1991-03-01 0 1991-04-01 8 1991-05-01 0 1991-06-01 5 1991-07-01 0 1991-08-01 6 1991-09-01 0 1991-10-01 2.99950 1991-11-01 2.99950 1991-12-01 2.99950 1992-01-01 2.99950 1992-02-01 2.99950 1992-03-01 2.99950 1992-04-01 2.99950 1992-05-01 2.99950 1992-06-01 2.99950 1992-07-01 2.99950 1992-08-01 2.99950 1992-09-01 2.99950 The red marked forcast values should be different and some should be zero,because it is an intermittent series,it has zero demand in the historic data,so it should have zero demand in the forecast,but it doesn't,i want to know why? According to your reply ,i try to understand that it decomped into 2 components: 1. the periods with non_zero demand below: date qty 1990-06-01 3 1990-09-01 3 1990-12-01 6 1991-02-01 7 1991-04-01 8 1991-06-01 5 1991-08-01 6 2. the number of periods between 2 non-zero demand below: date periods between 2 non-zreo demand 1990-06-01 5 1990-09-01 3 1990-12-01 3 1991-02-01 2 1991-04-01 2 1991-06-01 2 1991-08-01 2 3. then it has calculated a sequence ratio below,which is equal to qty/periods between 2 non-zreo demand: 1990-06-01 0.6 1990-09-01 1 1990-12-01 2 1991-02-01 3.5 1991-04-01 4 1991-06-01 2.5 1991-08-01 3 4. it gives the predict according to the sequence ratio series,and it seems to use ESM model to forecast,so if i set the lead time=12,all the forecast values are the same? Look forward to your advice. thanks, amy_q
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