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Creating formula using dynamic variables in for loop

Hi All
I did that one time, and it was painfully but I lost the script and the memory of that. Below what I am trying to do:

Tweak_List = dt_Temp << Get Column Names("String");

for(i = 1, i <= N Items(Tweak_List),i++,

 

a = Left(Tweak_List[i], Length(Tweak_List[i]) - 1) || "Δ";

b = Tweak_List[i];

c = Left(Tweak_List[i], Length(Tweak_List[i]) - 2);

 

dt << New Column( Left(Tweak_List[i], Length(Tweak_List[i]) - 1) || "Δ", Numeric, Continuous, Formula( if(:name1 == :name2, c - b, 0 ))));

 

);

 

In dt I have columns named ColName_2 and ColName, the Tweak_List is the list of names of columns like ColName_2.
I need do create a new Delta Column named ColName_Δ for each pair and have the formula  ColName - ColName_2 in it is a condition is meet.
I remember I was working with Eval and Co, but I forgot. Pls help me

 

Automation and ScriptingRe: Creating formula using dynamic variables in for loop

And as usual, finally I got one solution, fell free to replay with more efficient script.

For(i = 1, i <= N Items(Tweak_List), i++, 
 
 Eval(
  Eval Expr(
   dt << New Column(Left(Tweak_List[i], Length(Tweak_List[i]) - 1) || "Δ",
    Numeric,
    "Continuous",
    Formula(
     If(:ENTITY == :ENTITY_2,
      As Column(Expr(Char(Left(Tweak_List[i], Length(Tweak_List[i]) - 2)))) - As Column(Expr(Char(Tweak_List[i]))),
      0
     )
    )
   )
  )
 );
 
);

 

From iH: https://community.jmp.com/t5/JSL-Cookbook-Archived/Insert-one-expression-into-another-using-Eval-Insert-Eval-Expr/ta-p/48998 

Re: Creating formula using dynamic variables in for loop

You could use Word() or Words() instead of Left().

Names Default To Here(1);

dt = New Table("Untitled 143",
 Add Rows(1),
 Compress File When Saved(1),
 New Column("Column1", Numeric, "Continuous", Format("Best", 12), Set Values([1])),
 New Column("Column1_2", Numeric, "Continuous", Format("Best", 12), Set Values([2])),
 New Column("Column2", Numeric, "Continuous", Format("Best", 12), Set Values([3])),
 New Column("Column2_2", Numeric, "Continuous", Format("Best", 12), Set Values([4]))
);

tweaklist = {"Column1_2", "Column2_2"};

For Each({col_name}, tweaklist,
 Eval(EvalExpr(
  dt << New Column(Word(1, col_name, "_") || "_Δ", Numeric, Continuous, Formula(
   Expr(Name Expr(As Column(col_name))) - Expr(Name Expr(As Column(Word(1, col_name, "_"))))
  ));
 ));
);

Also if you don't need the formula but just the values, you could use << Set Each Value which doesn't need as heavy evaluation 

For Each({col_name}, tweaklist,
 dt << New Column(Word(1, col_name, "_") || "_Δ", Numeric, Continuous, << Set Each Value(
  As Column(col_name) - As Column(Word(1, col_name, "_"))
 ));
);