# Re: st: RE: Percentiles: Identify of smallest observation closetto percentile value

 From Rod Hunter To statalist@hsphsun2.harvard.edu Subject Re: st: RE: Percentiles: Identify of smallest observation closetto percentile value Date Tue, 04 Feb 2003 06:33:58 +1100

Thanks Nick and Ronnie.
I still don't appear to be out of the woods.

1.
I applied Nick's procedure to my example:
. centile var1 , c(75)
--------------------------------------------------------------------
-- Binom. Interp. --
Variable Obs Percentile Centile [95% Conf. Interval]

var1 4 75 9.75 7.45 10*

* Lower (upper) confidence limit held at minimum (maximum) of sample
-----------------------------------------------------------
. ret li
------------------------------------------------
scalars:
r(n_cent) = 1
r(N) = 4
r(ub_1) = 10
r(lb_1) = 7.450000000008672
r(c_1) = 9.75
macros:
r(centiles) : "75"
-------------------------------------------------
. list var1 if var1 == `r(c_1)'
-----------------------------------------------
var1
.
-----------------------------------------------
This does not give me the identity nor value of the largest observation within the percentage of the observations included by the 75th percentile.

2.
I tried Ronnie's approach:

. sum var1, d
-------------------------------------------
var1
Percentiles Smallest
1% 7 7
5% 7 8
10% 7 9 Obs 4
25% 7.5 10 Sum of Wgt. 4

50% 8.5 Mean 8.5
Largest Std. Dev. 1.290994
75% 9.5 7
90% 10 8 Variance 1.666667
95% 10 9 Skewness 0
99% 10 10 Kurtosis 1.64
---------------------------------------------------
. local macro*
. list var1 if var1 == `p75'
-------------------------------------------------
var1
-------------------------------------------------

3.
This is what I have been using:

. _pctile var1,p(75)
. gen var1_p75=r(r1)
. tabstat var1 if var1==var1_p75, stat(max)
-------------------------------------
no observations
-------------------------------------
alternatively:
. list var1 if var1==var1_p75
---------------------------------------
var1
---------------------------------------

Any further suggestions?

Regards,

Rod Hunter

Nick Cox wrote:

```Rod Hunter

```
```A simple eg. will suffice.

Obs. Var1
----------
1     	10
2	9
3	8
4	7
-----------

I would like Stata to tell me the value of the observation
that is at or
below the 75th percentile point, and to yield the identity (or
identities) of the observation(s).
```
```
I'll change your example. I don't know about "below". ~ 75% are
below; do you what them all?

. use auto
. centile rep78 , c(75)

-- Binom.
Interp. --
Variable |     Obs  Percentile      Centile        [95% Conf.
Interval]
-------------+--------------------------------------------------------
-----
rep78 |      69         75             4               4
5

. ret li

scalars:
r(n_cent) =  1
r(N) =  69
r(ub_1) =  5
r(lb_1) =  4
r(c_1) =  4

macros:
r(centiles) : "75"

. list rep78 if rep78 == `r(c_1)'

+-------+
| rep78 |
|-------|
5. |     4 |
15. |     4 |
24. |     4 |
29. |     4 |
30. |     4 |
|-------|
33. |     4 |
35. |     4 |
38. |     4 |
47. |     4 |
55. |     4 |
|-------|
56. |     4 |
58. |     4 |
59. |     4 |
62. |     4 |
63. |     4 |
|-------|
70. |     4 |
72. |     4 |
73. |     4 |
+-------+
Nick
n.j.cox@durham.ac.uk

*
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```
```
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```