Hi all,

I have a question about how to extract numbers and operation symbols from a string variable in Stata.

My data look as below:

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str19 packing
"20s*2"          
"10s x 3"        
""               
""               
"950gx2"         
"20s x 2"        
"20s x 2"        
"20s x 2"        
"100s"           
"10s"            
""               
"20s x 2"        
"16s"            
""               
""               
"18s x 2"        
"700ml"          
""               
"20s x 2"        
"500g"           
""               
"16s"            
"700ml"          
"700ml+200ml x 2"
"20ml x 6pcs"    
"16s"            
""               
"525ml x 2"      
"700ml"          
"950gx2"         
end

What I want is the total unit of the products, for instance for "20s*2"，I want to have 20*2=40; while for "700ml+200ml x 2" I want to get 1100. I don't know how to extract both the numbers and the operation symbols so that I can get the total amount of the units of the product.

I wonder if anyone has any suggestions with respect to this issue?

Thank you very much.