topic Re: Impute missing date using LOCF in SAS Procedures

Impute missing date using LOCF

JessSun — Wed, 12 Jun 2013 15:12:20 GMT

Hi everyone,

I have a sample dataset as follows:

id weight1 weight2 weight3 weight4

1 50.1 51.8 . 53.6

2 70.8 . . .

3 . 49.8 52.9 .

4 . 68.1 . 66.9

5 48.0 49.1 . .

I have tried the command as below,

data locf;

set tweight;

array weight

weight:;

do i=1 to dim(weight);

if weight=. then weight=weight[i-1];

end;

drop i;

run;

Then the output is as follows:

id weight1 weight2 weight3 weight4

1 50.1 51.8 51.8 53.6

2 70.8 70.8 70.8 70.8

BUT that is not what I expected because there are all missing after id 2. :smileyconfused::smileyconfused:

I am trying to amend the command......and produce the output as below,

id weight1 weight2 weight3 weight4

1 50.1 51.8 51.8 53.6

2 70.8 70.8 70.8 70.8

3 . 49.8 52.9 52.9

4 . 68.1 68.1 66.9

5 48.0 49.1 49.1 49.1

I think I missed ONE "if XXXXXX" or "else XXXXXX"~Please help~:smileyplus:

Re: Impute missing date using LOCF

Reeza — Wed, 12 Jun 2013 15:31:15 GMT

I think you need to add a condition to not check the first one, probably the easiest way, start your loop from two probably?

data locf;

set tweight;

array weight

weight:;

do i=2 to dim(weight);

if weight=. then weight=weight[i-1];

end;

drop i;

run;

Re: Impute missing date using LOCF

art297 — Wed, 12 Jun 2013 15:32:34 GMT

Change your loop to start at 2 rather than 1.

Re: Impute missing date using LOCF

JessSun — Wed, 12 Jun 2013 15:59:21 GMT

Thanks Reeza and Arthur!

What if one of the id (id 10) has only one observation as follows;

id weight1 weight2 weight3 weight4

9 . 41.7 41.7 40.8<-------i.e. Only keep the first one as missing value

10 . . . 49.0<-------i.e. Trying to keep the missing for the first three~:smileyconfused:

11 48.1 48.1 48.1 46.5

Re: Impute missing date using LOCF

Reeza — Wed, 12 Jun 2013 16:13:14 GMT

What's the output you get vs the output you want?

If it looks back and its missing it will stay missing.

Re: Impute missing date using LOCF

robertrao — Fri, 14 Jun 2013 19:41:01 GMT

Hi,

I am curious to know why the records dont show up when use :

do i= 1 to dim(weight)???

Thanks

Re: Impute missing date using LOCF

Reeza — Fri, 14 Jun 2013 20:29:10 GMT

Let's say i=1.

if weight[1]=. then weight[1]=weight[1-1];

which is:

if weight[1]=. then weight[1]=weight[0];

You don't have a weight[0] so SAS is writing errors to your log, I'd bet.

Check your log when you submit that code.