topic Re: Randomization in SAS Procedures

Randomization

jeewakamendis — Sat, 29 Nov 2014 12:25:24 GMT

Hi Everyone,

Please help me with the below randomization.

3 types of injections (A, B and C) are randomised to 3 locations in each arm (L1 L2 L3 R1 R2 R3).

L and R corresponds to LEFT AND RIGHT arms respectively.

For each arm, A has to be given at least once, remaining two locations in each arm can be allocated to either B or C.

It can both be B. Also It can both be C or It can be B and C.

I use PROC PLAN to generate random numbers and writing it to a SAS dataset.

Thanks in advanced.

This is what I got to so far.

proc plan seed=1832577;

factors a=20 b=6;

output out = c;

run;

%macro calc;

data dat(keep = SubjectNr Location arm Treatment allocatedarm allocatedarm2 allocatedarm3 allocTr1 allocTr2 allocTr3);

length Treatment $8.;

length Location $2.;

length arm $5;

set c;

retain ct ctt allocatedarm allocatedarm2 allocatedarm3 allocTr1 allocTr2 allocTr3;

if ct = . or ct ne a then do;

ct = a; ctt = 0; end;

ctt = ctt + 1;

if b<= 3 then do;

arm='right';

end;

else

arm='left';

if ctt=1 then do;

treatment = 'A';

allocatedarm=arm;

allocTr1= treatment;

end;

if ctt=2 then do;

if arm ne allocatedarm then do;

treatment = 'A'; end;

else do;

treatment = 'B or C';

end;

allocatedarm2=arm;

allocTr2 = treatment;

end;

if ctt=3 then do;

if (allocTr1 eq allocTr2) or (allocatedarm eq allocatedarm2) then

treatment = 'B or C';

if (allocatedarm eq allocatedarm2) and (arm ne allocatedarm) then

treatment = 'A';

allocatedarm3=arm;

allocTr3 = treatment;

end;

if ctt=4 then do;

if (arm ne allocatedarm) and (allocatedarm2 ne allocatedarm) and (allocatedarm3 ne allocatedarm) then

treatment = 'A';

end;

SubjectNr = a;

location = b;

run;

/* proc sort data = dat out = dat; by SubjectNr; run; */

ods rtf file = " .rtf";

footnote "";

proc print data = dat noobs;

var SubjectNr Location Treatment arm allocatedarm allocatedarm2 allocatedarm3 allocTr1 allocTr2 allocTr3;

run;

ods rtf close;

%mend;

%calc;

quit;

Re: Randomization

Patrick — Sun, 30 Nov 2014 00:38:43 GMT

If I understood your requirements right then below code should do what you're after.

proc plan seed=1832577;

factors Subj=20 Loc=6;

output out = Plan;

run;

proc format;

value arm

1-3 ='Right'

4-6 ='Left'

;

picture Location

1-3 = '00000000' (prefix='R')

4-6 = '00000000' (prefix='L')

;

run;

data _null_;

set Plan end=last;

SubjectNr=put(Subj,z10.);

Location=put(Loc,Location2.);

Arm=put(Loc,arm5.);

length Treatment $8;

if _n_=1 then

do;

dcl hash h1(multidata:'y',ordered:'yes');

_rc=h1.defineKey('SubjectNr','Arm','Treatment');

_rc=h1.defineData('SubjectNr','Arm','Treatment','Location');

_rc=h1.defineDone();

end;

Treatment='A';

if h1.check() ne 0 then

do;

_rc=h1.add();

end;

else

do;

if ceil(ranuni(1832577)*2)=1 then Treatment='B';

else Treatment='C';

_rc=h1.add();

end;

if last then

do;

_rc=h1.output(dataset:'want');

end;

run;

Re: Randomization

jeewakamendis — Thu, 04 Dec 2014 14:07:06 GMT

Thanks Patrick for this

Re: Randomization

Babloo — Thu, 04 Dec 2014 16:16:45 GMT

May I request you to tell me how ranuni works here as i confused with seeds'1832577'?

ceil(ranuni(1832577)*2

Re: Randomization

vkorsz — Thu, 04 Dec 2014 18:03:21 GMT

Ranuni returns a random number from the uniform distribution between 0 and 1. So it looks like here, the phrase

ceil(ranuni(1832577)*2)

will return 0 when the random number generated is 0,

1 when the random number generated is greater than 0 and less than or equal to .5,

and 2 when the random number generated is greater than .5 and less than or equal to 1.

The seed is specified here just to give a reproducible result. If you do not specify a seed, the results will change each time the code is run. The seed can be any number less than 2^31-1, including a date or time value as those are stored as numeric values in SAS.