Re: Simulation problem of normal distributed data

On 29 July 2014 23:25, Navin Goyal <[email protected]> wrote: > Hi Sheng, > I don't know the exact reason behind such mysterious behavior but if you > just change the seed number (the UNIFORM seed) it works. > e.g. I changed the seed# from 7545 to 17545 and was able to simulate > 1000 rows for the subject. > > $SIMULATION (6446) (*1*7545 UNIFORM) ONLYSIM NOPRED SUB=1 > > Its a rare occurrence but may be the seed number caused some issue (while > generating sufficient samples to satisfy the constraints you set up using > the DOWHILE LOOP). For example I think the same seed number (7545) may > work when the DOWHILE condition is reversed > (RL .*LT*. PRN) however it may not be appropriate based on your problem. > .......or may be there is some other explanation to such occurrence. > > Kind regards > Navin Goyal > > > > > > > On Tue, Jul 29, 2014 at 10:54 AM, Gerry Sheng <[email protected]> wrote: > >> Dear NMuser, >> >> I encountered a strange problem when I used the following code to >> simulate normal distributed data. When the data records >797, no result >> appears with NONMEM run into an infinite loop . But when the records >> decreasing to 796 (delete the last row), the results will occurred >> immediately. Anyone else met this phenomenon? Any comments and suggestions >> are appreciated. Thank you in advance. >> >> $PROBLEM PD >> $INPUT ID,CONC,DV >> $DATA data.csv IGNORE=@ ; >> >> $PRED >> NMEAN=THETA(1)+ETA(1) >> SD=THETA(2) >> >> ;Simulate count >> IF (ICALL.EQ.4) THEN >> N=0 >> PRN=0 >> CALL RANDOM(2, R) >> RL=1-R >> DO WHILE (RL .GT. PRN) >> LNNOR=LOG(6.283185)+2*LOG(SD)+((N-NMEAN)/SD)**2 >> PY=EXP(-0.5*LNNOR) >> PRN=PRN+PY >> IF (PRN .LT. RL) N=N+1 >> ENDDO >> DV=N >> ENDIF >> >> $THETA >> (30,41.7,60) ;MEAN >> (2,14.4,50) ;SD >> >> $OMEGA >> 0 FIX ;MEAN >> >> $SIMULATION (6446) (7545 UNIFORM) ONLYSIM NOPRED SUB=1 >> $TABLE ID TIME DV ONEHEADER NOPRINT FILE=npctab1.dta >> >> data.csv like this >> ID CONC DV >> 1 0 . >> 1 0 . >> 1 0 . >> 1 0 . >> 1 0 . >> 1 0.01 . >> 1 0.01 . >> 1 0.01 . >> 1 0.01 . >> 1 0.01 . >> ..... >> >> Yucheng Sheng >> >> Research Associate >> School of Pharmacy, UCL >> > > > > -- > Navin Goyal >