Inserting blank rows at specific observations in dataset

[David Smerdon]

I am trying to manipulate a text (.tex) document (a multiple-choice exam) in Stata, which I realize is a bit strange. I have copied the text to the data editor so that each line is an observation for the variable v1. I have found Stata quite handy for text manipulation, but I am stuck on one issue: I need to duplicate specific blocks of four observations (the MCQ choices) and insert them directly below the original, so that I can manipulate the correct answer. To do this, I thought to start by inserting four blank rows after each question, and then doing a replace. However, I haven't found a way to do this, including through the ingap command.

It is possible to identify each MCQ using strmatch because each question-line begins with "\mc", and likewise the block of choices ends with the same value "\end{MC}". Here is a snippet of the data:

* Example generated by -dataex-. To install: ssc install dataex
clear
input str145 v1
"%Label1: "                                                                                                                                      
"\mc The production possibility curve (PPC) represents the \_\_\_\_\_\_\_\_ combinations of goods that can be produced with available resources."
"\begin{MC}"                                                                                                                                     
"\item minimum attainable"                                                                                                                       
"\item maximum attainable"                                                                                                              
"\item only"                                                                                                                                     
"\item equitable"                                                                                                                                
"\end{MC}"                                                                                                                                       
"%Label2: "                                                                                                                                      
"\mc A point on the production possibility curve (PPC) is \_\_\_\_ if it is outside of the curve."                                     
"\begin{MC}"                                                                                                                                     
"\item attainable and efficient"                                                                                                                 
"\item attainable and inefficient"                                                                                                               
"\item unattainable"                                                                                                                             
"\item \textbf{None of the above}"                                                                                                               
"\end{MC}"                                                                                                                                       
end

I would like to manipulate the data so that it would now be:

* Example generated by -dataex-. To install: ssc install dataex
clear
input str145 v1
"%Label1: "                                                                                                                                      
"\mc The production possibility curve (PPC) represents the \_\_\_\_\_\_\_\_ combinations of goods that can be produced with available resources."
"\begin{MC}"                                                                                                                                     
"\item minimum attainable"                                                                                                                       
"\item \textbf{maximum attainable}"                                                                                                              
"\item only"                                                                                                                                     
"\item equitable"                                                                                                                                
"\end{MC}"    
"\begin{MC}"                                                                                                                                     
"\item minimum attainable"                                                                                                                       
"\item \textbf{maximum attainable}"                                                                                                              
"\item only"                                                                                                                                     
"\item equitable"                                                                                                                                
"\end{MC}"                                                                                                                                              
"%Label2: "                                                                                                                                      
"\mc A point on the production possibility curve (PPC) is \_\_\_\_\_\_\_\_\_ if it is outside of the curve."                                     
"\begin{MC}"                                                                                                                                     
"\item attainable and efficient"                                                                                                                 
"\item attainable and inefficient"                                                                                                               
"\item unattainable"                                                                                                                             
"\item \textbf{None of the above}"                                                                                                               
"\end{MC}"                                
"\begin{MC}"                                                                                                                                     
"\item attainable and efficient"                                                                                                                 
"\item attainable and inefficient"                                                                                                               
"\item unattainable"                                                                                                                             
"\item \textbf{None of the above}"                                                                                                               
"\end{MC}"                                                                                                                                         
end

[Andrew Musau]

To do this, I thought to start by inserting four blank rows after each question, and then doing a replace.

I am not sure I get what you want to achieve, but here is a way to create 4 blank observations (not rows!) after each block.

gen id=_n
gen toexpand=cond(strpos(v1,"\end{MC}")& v1[_n+1]!="" , 5,1)
expand toexpand, gen(new)
sort id new
replace v1= "" if new

Res.:

. l v1, sep(1)

     +------------------------------------------------------------------------------------------------------------------------------------+
     | v1                                                                                                                                 |
     |------------------------------------------------------------------------------------------------------------------------------------|
  1. | %Label1:                                                                                                                           |
     |------------------------------------------------------------------------------------------------------------------------------------|
  2. | \mc The production possibility curve (PPC) represents the \_\_\_\_\_\_\_\_ combinations of goods that can be produced with avail.. |
     |------------------------------------------------------------------------------------------------------------------------------------|
  3. | \begin{MC}                                                                                                                         |
     |------------------------------------------------------------------------------------------------------------------------------------|
  4. | \item minimum attainable                                                                                                           |
     |------------------------------------------------------------------------------------------------------------------------------------|
  5. | \item maximum attainable                                                                                                           |
     |------------------------------------------------------------------------------------------------------------------------------------|
  6. | \item only                                                                                                                         |
     |------------------------------------------------------------------------------------------------------------------------------------|
  7. | \item equitable                                                                                                                    |
     |------------------------------------------------------------------------------------------------------------------------------------|
  8. | \end{MC}                                                                                                                           |
     |------------------------------------------------------------------------------------------------------------------------------------|
  9. |                                                                                                                                    |
     |------------------------------------------------------------------------------------------------------------------------------------|
 10. |                                                                                                                                    |
     |------------------------------------------------------------------------------------------------------------------------------------|
 11. |                                                                                                                                    |
     |------------------------------------------------------------------------------------------------------------------------------------|
 12. |                                                                                                                                    |
     |------------------------------------------------------------------------------------------------------------------------------------|
 13. | %Label2:                                                                                                                           |
     |------------------------------------------------------------------------------------------------------------------------------------|
 14. | \mc A point on the production possibility curve (PPC) is \_\_\_\_ if it is outside of the curve.                                   |
     |------------------------------------------------------------------------------------------------------------------------------------|
 15. | \begin{MC}                                                                                                                         |
     |------------------------------------------------------------------------------------------------------------------------------------|
 16. | \item attainable and efficient                                                                                                     |
     |------------------------------------------------------------------------------------------------------------------------------------|
 17. | \item attainable and inefficient                                                                                                   |
     |------------------------------------------------------------------------------------------------------------------------------------|
 18. | \item unattainable                                                                                                                 |
     |------------------------------------------------------------------------------------------------------------------------------------|
 19. | \item \textbf{None of the above}                                                                                                   |
     |------------------------------------------------------------------------------------------------------------------------------------|
 20. | \end{MC}                                                                                                                           |
     +------------------------------------------------------------------------------------------------------------------------------------+

[Mike Lacy]

I recently learned about the built-in -insobs- (insert observations) command, which might also be useful here.

[Chen Samulsion]

The command -insobs- seems to be introduced from Stata 14. Type -which insobs- get the following (part):

*! version 1.0.2  10mar2015

[David Smerdon]

-insobs- didn't seem to work for my (admittedly rare) purposes, which is to insert observations depending on matching a string. But Andrew's code works perfectly - thanks!