Coding to re-arrange variables

[desireatem]

Hello I have this data with four variables A, B, C D that I want to make it one variable A. THe data is as such.

A              B             C           D

1               1             1            .

2              1             .             1

.               2             1            .

.                .             2            .

.                .              .           3

I want to create this data with one variable call A as above

F

1

2

2

3

The variable A B C D are in order and F takes the first number. If  all are missing, F will be missing otherwise F takes the first value from the variable A, B, C, D.

[desireatem]

Actually F is: F

F

1

2

2

2

3

[Patrick · Accepted solution]

The coalesce() function will pick the first non-missing value.

data sample;
  input A B C D;
  F=coalesce(a,b,c,d);
datalines;
1 1 1 .
2 1 . 1
. 2 1 .
. . 2 .
. . . 3
;