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Re: pairing unpaired data [was: Re: st: any idea?]


From   "Y.R.E. Retamal" <[email protected]>
To   [email protected]
Subject   Re: pairing unpaired data [was: Re: st: any idea?]
Date   Tue, 07 Jan 2014 19:20:05 +0000

Dear Nick

Thanks a lot for your soon response. The method is no more than showed. I have to add other variables like width and height for the same bone. So, if three variables match, probably both bones would be from the same skeleton. I would expect that many bones would not match between them, so I could discard them being from the same skeleton. Problems would appear if e.g. a right bone matches with more than one left bone. But at least I could simplify the work and after I could focus on problematic cases.

Rodrigo






On 2014-01-07 18:49, Nick Cox wrote:
I changed the thread title, which was not informative.

You need a method. Some predictable pitfalls are that for some bones
there is no acceptable match and that others there could be two or
more acceptable matches. I don't think there is a canned solution
independent of your spelling out what the method is.

Nick
[email protected]


On 7 January 2014 18:20, Y.R.E. Retamal <[email protected]> wrote:
Thank you very much Eric and Nick for the advices.

I will try to give a clearer idea of what want to do:
For example I have the following database of human bones. I removed missing
values of length for a better understanding:

id      type    side    length          id      type    side    length
1       femur   left    18              21      humerus left    13
2       femur   left    65.85           22      humerus left    56
3       femur   left    69.1            23      humerus left    92
4       femur   left    130             24      humerus left    126
5       femur   left    131.2           25      humerus left    154
6       femur   left    143             26      humerus left    170
7       femur   left    145             27      humerus left    198
8       femur   left    160             28      humerus left    228
9       femur   left    183             29      humerus left    230
10      femur   left    200             30      humerus left    232
11      femur   right   28              31      humerus right   238
12      femur   right   80              32      humerus right   10
13      femur   right   96.5            33      humerus right   66
14      femur   right   126             34      humerus right   123
15      femur   right   127             35      humerus right   128
16      femur   right   128             36      humerus right   143
17      femur   right   138             37      humerus right   200
18      femur   right   146             38      humerus right   228
19      femur   right   148             39      humerus right   230
20      femur   right   200             40      humerus right   241

These data belong to a commingled skeletal collection and some right bones (femurs and humerus respectively) should match with a left bone, but I do not know which bones match. Following the idea that a right bone from a same skeleton should have the same length (approximately) with its respective left bone, I want to subtract each right femur to each left femur, with the aim to find which right femur matches with a left femur, i.e. have the same or almost the same length, so the subtraction would be zero or near zero.
The same proceeding with the humerus (and other bones).

If you have any idea to perform this, please let me know.

Rodrigo



Best wishes

Rodrigo





On 2014-01-05 23:54, Nick Cox wrote:

<>

Eric Booth gives very good advice.

Your problem with the link to the Stata Journal file you were directed
to me may be just that you didn't step past the standard material
bundled with every reprint file.

Nick
[email protected]


On 5 January 2014 21:03, Eric Booth <[email protected]> wrote:

<>

The Stata Journal link you mention that Nick sent you works for me. The title of the article is "Stata tip 71: The problem of split identity, or how to group dyads” by Nick J. Cox, so maybe you can google that title if your
browser isn’t navigating to it properly.



Your example dataset doesn’t align with your desired dataset.

How do we know what is x and what is j in the first 20 obs of your
example data (see below) (also note the Statalist FAQ about not sending
attachments) ?

You need some kind of identifier that ties, for example, obs or id 1
(even though it’s missing) to the other right side femur observation of
interest (is it id 7 or id 9 or ??).


**your example data:

id      type    side    length
1       femur   right
2       femur   left
3       femur   right
4       femur   left
5       femur   right   373
6       femur   left    416
7       femur   right   138
8       femur   left
9       femur   right   270
10      femur   left
11      femur   left
12      femur   right
13      femur   left
14      femur   right
15      femur   left    281
16      femur   right
17      femur   left    160
18      femur   left
19      femur   right
20      femur   left


We can’t just sort by ‘type’ and ‘side’ to get a dataset of the same
structure as you presented initially, so I think you need to provide more information about this. (also, if the rule is, as you imply, to sort by type and side and then subtract every third observation from each other then
what do we do with missing 'length' and missing ‘side’?)

If the rule is that id 1 and id 2 are a pair then whey does the
left/right ordering suddenly change starting around id 17?

- Eric




On Jan 5, 2014, at 2:46 PM, Y.R.E. Retamal <[email protected]> wrote:

Dear Guys

Some weeks ago, Red Owl and Nick helped me with some loops for my work.
I have tried to run some suggestion in my dataset, but I had some
difficulties.
I give you the basic structure of my dataset and my question:

I want to create some new variables containing the difference between
the length of two individuals from different groups:

id     side     length      newvar1       newvar2      newvar3
1      right      x           x-j           x-k          x-l
2      right      y           y-j           y-k          y-l
3      right      z           z-j           z-k          z-l
4      left       j           j-x           j-y          j-z
5      left       k           k-x           k-y          k-z
6      left       l           l-x           l-y          l-z

Red Owl suggested me following this example:

*** BEGIN CODE ***
* Build demo data set.
clear
* Length is capitalized to distinguish from length().
input id str5(side) Length
1 right 10
2 right 15
3 right 11
4 left  13
5 left  10
6 left  12
end
gen byte newvar1 = .
forval i = 1/3 {
 replace newvar1 = Length[`i'] - Length[4] in `i'
 }
forval i = 4/6 {
 replace newvar1 = Length[`i'] - Length[1] in `i'
 }
gen byte newvar2 = .
forval i = 1/3 {
 replace newvar2 = Length[`i'] - Length[5] in `i'
 }
forval i = 4/6 {
 replace newvar2 = Length[`i'] - Length[2] in `i'
 }
gen byte newvar3 = .
forval i = 1/3 {
 replace newvar3 = Length[`i'] - Length[6] in `i'
 }
forval i = 4/6 {
 replace newvar3 = Length[`i'] - Length[3] in `i'
 }
list, noobs sep(0)
*** END CODE ***


However, my dataset is much more longer and is difficult to perform it.
I hope you can help me giving me more ideas.
I send you an extract of my dataset in .xlsx format
Also, the webpage suggested by Nick to review the discussion about the topic (http://www.stata-journal.com/sjpdf.html?articlenum=dm0043) redirects me to a non-sense file to download. Please give me the number of the journal
to read the discussion.

Happy new year to all of you

Rodrigo


On 2013-12-15 22:39, Y.R.E. Retamal wrote:

Dear Red Owl and Nick
Thank you very much for your response. The code works perfectly, just
as I need.
Best wishes
Rodrigo
On 2013-12-14 22:31, Nick Cox wrote:

In addition to Red's helpful suggestions, note that technique for such
paired data was discussed in
http://www.stata-journal.com/sjpdf.html?articlenum=dm0043
which is publicly accessible. The problem is that the identifiers in Rodrigo's example appear to make little sense. How is Stata expected
to know that 1 and 4, 2 and 5, 3 and 6 are paired? Perhaps the
structure of the dataset is clearer in practice. If so, basic
calculations are just a couple of lines or so.
Nick
[email protected]
On 14 December 2013 15:33, Red Owl <[email protected]> wrote:

Rodrigo,
The following code demonstrates an approach with basic loops.
It could be made more efficient with a different loop
structure, but this approach may be more informative.
*** BEGIN CODE ***
* Build demo data set.
clear
* Length is capitalized to distinguish from length().
input id str5(side) Length
1 right 10
2 right 15
3 right 11
4 left  13
5 left  10
6 left  12
end
gen byte newvar1 = .
forval i = 1/3 {
 replace newvar1 = Length[`i'] - Length[4] in `i'
 }
forval i = 4/6 {
 replace newvar1 = Length[`i'] - Length[1] in `i'
 }
gen byte newvar2 = .
forval i = 1/3 {
 replace newvar2 = Length[`i'] - Length[5] in `i'
 }
forval i = 4/6 {
 replace newvar2 = Length[`i'] - Length[2] in `i'
 }
gen byte newvar3 = .
forval i = 1/3 {
 replace newvar3 = Length[`i'] - Length[6] in `i'
 }
forval i = 4/6 {
 replace newvar3 = Length[`i'] - Length[3] in `i'
 }
list, noobs sep(0)
*** END CODE ***
Good luck.
Red Owl
[email protected]

Y.R.E. Retamal" <[email protected]> Sat, 14 Dec 2013 12:08:42:
Dear list
I am very complicated trying to perform an analysis using STATA and
I

cannot find the way. Maybe you could help me. I want to create some
new
variables containing the difference between the length of two
individuals from different groups:

id     side     length      newvar1       newvar2      newvar3
1      right      x           x-j           x-k          x-l
2      right      y           y-j           y-k          y-l
3      right      z           z-j           z-k          z-l
4      left       j           j-x           j-y          j-z
5      left       k           k-x           k-y          k-z
6      left       l           l-x           l-y          l-z
I do not know if I do explain myself clearly, the individuals are

bones (clavicles, for example), so it is possible that some right clavicles pair-match with left clavicles, following the idea that an
individual has bone of similar length.

Any help could bring me a light!
Best wishes
Rodrigo

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