I don't understand what's wrong ! I work on an annual data file with 20 observations spanning from 1971 to1990 and create a dummy variable by using " loop for i=1971..1990 ". When looking at the printout, changes are reported for each iterations but finally, displaying the dummy variable I see no change . I replace the loop by "i=1..20" and it worked fine . Moreover, the time series plot doesn't show the usual graph's left margin, the thin fine-looking space between Y-axis and the drawing (see attached). Best, Artur --------------------------------- Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses. gretl version 1.6.2.1 Current session: 2007/05/08 16:29 ? genr sd_resid = sd(residuals) Generated scalar sd_resid (ID 7) = 2,92443 ? genr mark = (abs(residuals) > sd_resid) Generated series mark (ID 8) ? genr series mark_bis ? loop for i=1971..1990 loop: i = 1971 loop: i = 1972 loop: i = 1973 loop: i = 1974 mark_bis[i] = 1 loop: i = 1975 mark_bis[i] = 1 loop: i = 1976 loop: i = 1977 loop: i = 1978 loop: i = 1979 loop: i = 1980 loop: i = 1981 mark_bis[i] = 1 loop: i = 1982 loop: i = 1983 mark_bis[i] = 1 loop: i = 1984 loop: i = 1985 loop: i = 1986 loop: i = 1987 loop: i = 1988 loop: i = 1989 loop: i = 1990 mark_bis[i] = 1 Number of iterations: 20 ? genr series mark_tris ? loop i=1..20 loop: i = 1 loop: i = 2 loop: i = 3 loop: i = 4 mark_tris[i] = 1 loop: i = 5 mark_tris[i] = 1 loop: i = 6 loop: i = 7 loop: i = 8 loop: i = 9 loop: i = 10 loop: i = 11 mark_tris[i] = 1 loop: i = 12 loop: i = 13 mark_tris[i] = 1 loop: i = 14 loop: i = 15 loop: i = 16 loop: i = 17 loop: i = 18 loop: i = 19 loop: i = 20 mark_tris[i] = 1 Number of iterations: 20 ? print residuals mark mark_bis mark_tris --byobs Obs residuals mark mark_bis mark_tris 1971 1,197218 0 0 0 1972 2,670174 0 0 0 1973 -2,562178 0 0 0 1974 -5,389217 1 0 1 1975 -5,645469 1 0 1 1976 -2,006633 0 0 0 1977 0,363064 0 0 0 1978 1,540767 0 0 0 1979 0,016240 0 0 0 1980 -0,476465 0 0 0 1981 -3,045875 1 0 1 1982 -0,177509 0 0 0 1983 4,908354 1 0 1 1984 0,756328 0 0 0 1985 2,681048 0 0 0 1986 1,158102 0 0 0 1987 0,791340 0 0 0 1988 -2,879183 0 0 0 1989 0,851209 0 0 0 1990 5,248683 1 0 1