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# st: RE: histogram

 From Nick Cox To "'statalist@hsphsun2.harvard.edu'" Subject st: RE: histogram Date Thu, 14 Oct 2010 15:03:39 +0100

```This is almost the function of -egen, tag()-.

egen tag = tag(id)

But with your problem, it is better to go back to first principles:

bysort id (mean) : gen tag = _n == 1
histogram mean if tag

The step of sorting within -id- was what you were missing.

Nick
n.j.cox@durham.ac.uk

Schöler, Lisa

I have different observations within one id:

Example

+----------------------------------+
| id   mean(brand) brand  year   |
|--------------------------------|
|  1   5      		7     1999 |
|  1   5      		5     2000 |
|  1   5   		3     2001 |
|  1   5   		5     2002 |
|  1   .      		.     2003 |
|--------------------------------|
|  id   mean(brand) brand  year  |
|--------------------------------|
|  2   .      		.     1999 |
|  2   6      		7     2000 |
|  2   6   		8     2001 |
|  2   6   		5     2002 |
|  2   6      		4     2003 |
|--------------------------------|
|  id   mean(brand) brand  year  |
|--------------------------------|
|  2   .      		.     1999 |
|  2   6      		7     2000 |
|  2   6   		8     2001 |
|  2   6   		5     2002 |
|  2   6      		4     2003 |
+------------------------------+

Now I need to get a histogram that uses only one observation for each id for the mean(brand). Therefore I wanted to include a dummy=1, so I can use the command

. histogram if dummy==1

Can anybody help me how I can create a dummy=1 only for one observation per id? I was gonna use

. by id: gen dup = cond(_N==1,0,_n)

and then

. histogram if dup==1

But the problem here is that I have missings within my id groups, so sometimes my dup per id starts with 2.

If anybody has a better idea than creating a dummy, I am very happy to hear about it.

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```

• References:
• st: histogram
• From: Schöler, Lisa <lschoeler@wiwi.uni-frankfurt.de>