Common value in dummies

[ajay pasi]

Hi statalist community,

I need help in the following problem:


/*-------------------------------------------------------------------------------------------------------------*
|
|
I | have three dummies, D1, D2, and D3.
|
I | need D4
|
| Condition-a of D4: takes value 1 if either of D1 D2 D3 is 1
| Condition-b of D4: takes value 0 for all rows, in which D1 D2 D3 are not 1, with another condition that at least one of D1 D2 D3, is zero
| Condition-c of D4: takes value '.' missing value for all rows, in which D1 D2 D3, are all '.' missing values
|
*-----------------------------------------------------------------------------------------------------------------------------------------*/

[Hemanshu Kumar]

ajay pasi I'm not able to entirely figure out what you want D4 to do for each possible value of D1, D2 and D3. Perhaps you can show us a logic table?

[ajay pasi]

If Column_D1 takes value 0 or 1
If Column_D2 takes value 0 or 1
If Column_D3 takes value 0 or 1

Logic using three columns (i.e., Column_D1, Column_D2, Column_D3)	D4
If at least one of the three columns is 1	1
If all (three) columns are missing values	missing value
between three columns, at least column has 0 and other columns have missing value	0

[Hemanshu Kumar]

I think any of these serves your purpose:

gen byte D4 = (D1 == 1 | D2 == 1 | D3 == 1)
replace D4 = . if D1 == . & D2 == . & D3 == .

or

egen byte D5 = anymatch(D1 D2 D3), value(1)
replace D5 = . if D1 == . & D2 == . & D3 == .

or even just

gen byte D6 = max(D1, D2, D3)

Here are the results of all possible combinations of values of the three variables:

. li, noobs sep(0)
  +-----------------------------+
  | D1   D2   D3   D4   D5   D6 |
  |-----------------------------|
  |  0    0    0    0    0    0 |
  |  0    0    1    1    1    1 |
  |  0    0    .    0    0    0 |
  |  0    1    0    1    1    1 |
  |  0    1    1    1    1    1 |
  |  0    1    .    1    1    1 |
  |  0    .    0    0    0    0 |
  |  0    .    1    1    1    1 |
  |  0    .    .    0    0    0 |
  |  1    0    0    1    1    1 |
  |  1    0    1    1    1    1 |
  |  1    0    .    1    1    1 |
  |  1    1    0    1    1    1 |
  |  1    1    1    1    1    1 |
  |  1    1    .    1    1    1 |
  |  1    .    0    1    1    1 |
  |  1    .    1    1    1    1 |
  |  1    .    .    1    1    1 |
  |  .    0    0    0    0    0 |
  |  .    0    1    1    1    1 |
  |  .    0    .    0    0    0 |
  |  .    1    0    1    1    1 |
  |  .    1    1    1    1    1 |
  |  .    1    .    1    1    1 |
  |  .    .    0    0    0    0 |
  |  .    .    1    1    1    1 |
  |  .    .    .    .    .    . |
  +-----------------------------+

[ajay pasi]

From egen byte D4 = anymatch(D1 D2 D3), value(1)


say, if D1 is 0 and D2 is missing and D3 is missing. In this case, will the code produce 0 in D4?

[Hemanshu Kumar]

Yes. See the edited post in #4, which includes the results of all possible combinations of values.

[ajay pasi]

thanks Hemanshu.