Hi, I'm new to GRETL so please excuse the following naive question. How do I create a new variable in a script? Here's my problem. I have a monthly times series from 1960:1 to 2009:4. One variable is the monthly cpi. I merely want to calculate the percent change on an annual basis. I used the following: genr pct = (((cpi/lags(1, cpi))^12)-1)*100 and got gretl version 1.8.0 Current session: 2009/06/10 19:29 ? genr pct = (((cpi/lags(1, cpi))^12)-1)*100 Data types not conformable for operation Error executing script: halting What's wrong? What's conformability have to do with this? Conformable on what? Also, I did the following: genr lag = lags(1, cpi) and got gretl version 1.8.0 Current session: 2009/06/10 19:32 ? genr lag = lags(1, cpi) Generated list lag but lag was no where in my variable list, although cpi(-1) was. Can someone explain how variables are created? Any help is appreciated. Thanks, Walt -- ________________________ Walter R. Paczkowski, Ph.D. Data Analytics Corp. 44 Hamilton Lane Plainsboro, NJ 08536 ________________________ (V) 609-936-8999 (F) 609-936-3733 dataanalytics(a)earthlink.net www.dataanalyticscorp.com