How to use "if not" condition in regression

[Phuc Nguyen]

Hi all,

I read the syntax of regress and operators but still cannot find how to run a regression with a condition that: variable "INDC3" not equal to 'NA', 'UNCLS', 'UQEQS')
My original code below works well

areg wINV_DAY pt wFIRM_SIZE LNGDP UNEMPLOYMENT  INFLATION wTANGIBILITY  i.yr , a(TYPE2)

My code below caused error:

areg wINV_DAY pt wFIRM_SIZE LNGDP UNEMPLOYMENT  INFLATION wTANGIBILITY  i.yr if (INDC3 ~=('NA', 'UNCLS', 'UQEQS')) , a(TYPE2)

The error is:

'NA','UNCLS','UQEQS' invalid name
r(198);

When I changed from "~=" TO "!=" , the same error popping up.
Can you please help me to adjust the code to run the regression where INDC3 not equal to "NA", "UNCLS" or "UQEQS"?


Update:
I changed from single quotation to double quotation (

if (INDC3 ~=("NA", "UNCLS", "UQEQS"))

)and it works, but I am not sure whether it is a proper fix?

[Clyde Schechter]

if (INDC3 ~=("NA", "UNCLS", "UQEQS"))

is not legal Stata syntax. I'm surprised it does not give you an error message. In any case, after some experimentation, as best I can tell, it is not doing what you want it to: it is only testing whether INDC3 is unequal to "NA" and ignoring "UNCLS" and "UQEQS"

In any case, the solution to your problem is via the -inlist()- function. See -help inlist()- for details of how to use it.

[Phuc Nguyen]

Thank you Clyde Schechter
After a while with inlist(), I found the code below can be used:

!inlist(INDC3,"NA", "UNCLS", "UQEQS")

Warm regards.

[Joro Kolev]

What you figured out is the best way to go:

. sysuse auto, clear
(1978 Automobile Data)

. keep make

. keep in 1/4
(70 observations deleted)

. list if !inlist(make, "AMC Concord" , "AMC Pacer" )

     +---------------+
     | make          |
     |---------------|
  3. | AMC Spirit    |
  4. | Buick Century |
     +---------------+

An alternative and not so best is the following:

. list if make!="AMC Concord" & make!= "AMC Pacer"

     +---------------+
     | make          |
     |---------------|
  3. | AMC Spirit    |
  4. | Buick Century |
     +---------------+

And as Clyde said, it is a mystery what Stata does when you try your original logical but invalid syntax:

. list if make != ("AMC Concord", "AMC Pacer")

     +---------------+
     | make          |
     |---------------|
  2. | AMC Pacer     |
  3. | AMC Spirit    |
  4. | Buick Century |
     +---------------+

. dis ("AMC Concord", "AMC Pacer")
AMC Concord

. list if make != ("AMC Concord" | "AMC Pacer")
type mismatch
r(109);

Thank you Clyde Schechter
After a while with inlist(), I found the code below can be used:

!inlist(INDC3,"NA", "UNCLS", "UQEQS")

Warm regards.