duration between 2 dates

[noda6003]

I Have a dataset which has PID and 2 dates and i need duration taken from date STDT-EST(from same PID above EST).

This is the dataset 

DATA WORK.Book1;
    LENGTH
        PID              $ 12
        STDT               8
        EXEN               8
        EXD                8
        STDY               8
        EST                8
        GR               $ 8 ;
    FORMAT
        PID              $CHAR12.
        STDT             DATE9.
        EXEN             BEST12.
        EXD              BEST12.
        STDY             BEST12.
        EST              DATE9.
        GR               $CHAR8. ;
    INFORMAT
        PID              $CHAR12.
        STDT             DATE9.
        EXEN             BEST12.
        EXD              BEST12.
        STDY             BEST12.
        EST              DATE9.
        GR               $CHAR8. ;
    INFILE DATALINES4
        DLM='7F'x
        MISSOVER
        DSD ;
    INPUT
        PID              : $CHAR12.
        STDT             : BEST32.
        EXEN             : BEST32.
        EXD              : BEST32.
        STDY             : BEST32.
        EST              : BEST32.
        GR               : $CHAR8. ;
DATALINES4;
01-001-S0012.11122277no event
01-001-S0012222842108222843
01-001-S0012222852108222841
01-001-S0012222852108222842
01-001-S0012222872108222843
01-001-S0015.11122306no event
01-001-S001522313238223131
01-001-S0015.3301522320no event
01-001-S0015.4302222327no event
01-001-S00152233853029223341
01-001-S0015.6303622341no event
01-001-S001922354111223541
01-001-S0019.23822361no event
01-001-S0019.3101522368no event
01-001-S0025.11122389no event
;;;;

and i want something like below duration

PID	STDT	EXEN	EXD	STDY	EST	GR	ANL
01-001-S0012		1	1	1	28Dec2020	no event
01-001-S0012	04Jan2021	2	10	8	04Jan2021	3	value as 01jan2021-28dec2020
01-001-S0012	05Jan2021	2	10	8	04Jan2021	1	value as 05jan2021-04jan2021
01-001-S0012	05Jan2021	2	10	8	04Jan2021	2	value as 05jan2021-04jan2021
01-001-S0012	07Jan2021	2	10	8	04Jan2021	3	value as 07jan2021-04jan2021
01-001-S0015		1	1	1	26Jan2021	no event
01-001-S0015	02Feb2021	2	3	8	02Feb2021	1	value as 02Feb2021-26Jan2021
01-001-S0015		3	30	15	09Feb2021	no event
01-001-S0015		4	30	22	16Feb2021	no event
01-001-S0015	27Feb2021	5	30	29	23Feb2021	1	value as 27Feb2021-23Feb2021
01-001-S0015		6	30	36	02Mar2021	no event
01-001-S0019	15Mar2021	1	1	1	15Mar2021	1	Value as 15Mar2021-02Mar2021
01-001-S0019		2	3	8	22Mar2021	no event
01-001-S0019		3	10	15	29Mar2021	no event
01-001-S0025		1	1	1	19Apr2021	no event

[PaigeMiller · Accepted solution]

data want;
    set book1;
    by pid;
    prev_est=lag(est);
    if first.pid then anl=.;
    else anl=stdt-prev_est;
    drop prev_est;
run;

[Kurt_Bremser]

I'd use the IFN function:

data want;
set book1;
by pid;
anl = ifn(first.pid,.,stdt - lag(est));
run;

All arguments to IFN are evaluated before the condition in the first argument is applied, so LAG will always correctly fill its queue.