How to realize data deformation operation

[fu gang]

How to perform the following data operations as follows:

(1) Place the data scattered in multiple rows on one row

* Example generated by -dataex-. For more info, type help dataex
clear
input str2(a b c d)
"a"  ""   ""   ""  
""   "b"  ""   ""  
""   ""   "c"  ""  
""   ""   ""   "d" 
"fd" ""   ""   ""  
""   "fe" ""   ""  
""   ""   "fe" ""  
""   ""   ""   "ef"
"de" ""   ""   ""  
""   "ss" ""   ""  
""   ""   ""   ""  
""   ""   ""   "fw"
"cc" ""   ""   ""  
""   "fd" ""   ""  
""   ""   "ef" ""  
""   ""   ""   "ge"
end

My goal is to transform the data into the following data

(2) How to store the serial number of a specific value in a variable A, or how to store the value of another variable B corresponding to a specific value in a variable A for subsequent operations

The data are the same as aboveL

We want to store the serial number of the variable A when it is not empty, that is, the value of the corresponding variable obs ( the value of the red in the figure ), in the temporary element for subsequent data operations.

Looking forward to your reply, looking forward to your help, Thank you very much,

[Clyde Schechter]

I believe the following does what you want:

gen obs_no = _n
gen group_num = sum(!missing(a))
collapse (firstnm) obs_no a b c d, by(group_num)

[fu gang]

Thank you very much ,It's very king of you