[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

From |
Nick Cox <n.j.cox@stata.com> |

To |
Nick Cox <n.j.cox@stata.com> |

Subject |
Re: st: transform observations in variables |

Date |
Mon, 22 Sep 2008 16:31:01 -0500 |

An alternative is egen period1 = mean(size) if period == 1, by(familyname) bysort familyname (period1) : replace period1 = period1[1] So this can be generalised to forval i = 1/3 { egen period`i' = mean(size) if period == `i', by(familyname) bysort familyname (period1) : replace period`i' = period`i'[1] } That should deal more smoothly with repeats (if any) and gaps. Nick n.j.cox@durham.ac.uk Nick Cox wrote:

Consider -period- 1. Then

(period == 1) * size

is 0 when -period- is not 1 and -size- when -period- is 1. So

egen period1 = total((period == 1) * size), by(familyname)

should do the trick so long as -period- is 1 just once for each family.

Similarly, the other -period- values should fall to the same trick:

forval i = 1/3 {

egen period`i' = total((period == `i') * size), by(familyname)

}

Now one problem is apparent: family AB for example is not observed at

periods 2 and 3. So -period2- and -period3- will be 0 for that family.

If -size- can only be positive, then no problem: 0 means missing, and that can be fixed.

If -size- can be zero, then some other solution will be needed.

If each value of -period- can occur more than once for each family, then that is soluble, but I'll wait to hear that can happen.

Nick

permanent address:n.j.cox@durham.ac.uk

Fabian Brenner

My data look like the following:

"familiyname" "period" "size" "period1" "period2"

"period3"

AA 1 8

AA 2 7

AA 3 3

AB 1 4

BG 1 4

BG 2 8

For each "familyname" I want to get the values of "size" in the column

with the equivalent "period" (1 to 3). The values of "size" should be

written in the column of the equivalent period for all observations of

the same "familyname" (that is why I wasn't able to manage it with -if-)

The result should be:

"familiyname" "period" "size" "period1"

"period2" "period3"

AA 1 8 8

7 3

AA 2 7 8

7 3

AA 3 3 8

7 3

AB 1 2 2

BG 1 4 4

6

BG 2 6 4

6

* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: transform observations in variables***From:*Nick Cox <n.j.cox@stata.com>

- Prev by Date:
**RE: st: Modeling animal growth - nonlinear mixed model** - Next by Date:
**Re: st: Is there a "statistics coach" in Stata (like the one for SPSS)?** - Previous by thread:
**Re: st: transform observations in variables** - Next by thread:
**st: Correctly classified-lstat** - Index(es):

© Copyright 1996–2016 StataCorp LP | Terms of use | Privacy | Contact us | What's new | Site index |