dear everyone,

when i write in gretl the scripts

"
open greene22_2
discrete Z5
list X=dummify(Z5) --drop-first
"

then I run the program and get the results,

"
gretl version 1.9.92
Current session: 2015-03-14 16:31

? open greene22_2

Read datafile C:\Program Files\gretl\data\greene\greene22_2.gdt
periodicity: 1, maxobs: 601
observations range: 1 to 601

Listing 10 variables:
  0) const    1) Y        2) Z1       3) Z2       4) Z3     
  5) Z4       6) Z5       7) Z6       8) Z7       9) Z8     

? discrete Z5
? list X=dummify(Z5) --drop-first
> list X=dummify(Z5) --drop-
The symbol 'drop' is undefined

Error executing script: halting
> list X=dummify(Z5) --drop-first
"

why did i encounter the error?

best,

shi,qi