Impute missing date using LOCF

[JessSun]

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:

[Reeza · Accepted solution]

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;

[JessSun]

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

[Reeza]

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

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

[robertrao]

Hi,

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

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

Thanks

[Reeza]

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. 

[art297]

Change your loop to start at 2 rather than 1.