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Re: st: calculating many distances and storing them in many new variables


From   Yuval Arbel <yuval.arbel@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: calculating many distances and storing them in many new variables
Date   Fri, 21 Oct 2011 10:40:06 +0200

Anna,

I'm not sure what your precise goal is. But if your target is only to
map what hospital each patient went, may I suggest the following:

Suppose you have a column of coordinates under "patient" and another
column under "hospitals"
If you are working with STATA11 you can try running:

reg patient i.hospitals

Let me show you what is the output you get by using one of the
examples I ran: I collected a small dataset, which measures land
values (rent) and distance from Tel Aviv center (distance):

. reg rent i.distance

      Source |       SS       df       MS              Number of obs =      55
-------------+------------------------------           F(  9,    45) =   12.43
       Model |   294279904     9  32697767.1           Prob > F      =  0.0000
    Residual |   118368183    45  2630404.07           R-squared     =  0.7131
-------------+------------------------------           Adj R-squared =  0.6558
       Total |   412648087    54  7641631.24           Root MSE      =  1621.9

------------------------------------------------------------------------------
        rent |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
    distance |
       1000  |  -8245.833    1238.71    -6.66   0.000    -10740.72   -5750.943
       1500  |  -8087.026   1038.817    -7.78   0.000    -10179.31   -5994.741
       2000  |  -6353.833   1067.634    -5.95   0.000    -8504.158   -4203.509
       2500  |  -7560.333   1480.542    -5.11   0.000     -10542.3    -4578.37
       3000  |  -6545.958   1097.999    -5.96   0.000    -8757.442   -4334.475
       3500  |      -9500   1324.237    -7.17   0.000    -12167.15    -6832.85
       4000  |  -9891.905   1119.184    -8.84   0.000    -12146.06   -7637.752
       4500  |  -10258.33    1238.71    -8.28   0.000    -12753.22   -7763.443
       5000  |  -11600.33   1872.753    -6.19   0.000    -15372.25   -7828.414
             |
       _cons |   13433.33   936.3767    14.35   0.000     11547.37    15319.29
------------------------------------------------------------------------------

Note that the distance variable includes values from 500 to 5000
meters. The command made the 500 meter distance the base category.

On Fri, Oct 21, 2011 at 5:13 AM, Maria Ana Vitorino
<vitorino@wharton.upenn.edu> wrote:
> Dear StataList users,
>
> Suppose we have the following toy data which has a list with patients, the
> hospital to which they went (hosp_ch) and the coordinates for both.
>
> patient_id hosp_ch      lat_pat lng_pat lat_hosp        lng_hosp
> 1               a               2               4               5
>     6
> 2               a               1               3               5
>     6
> 8               c               3               5               10
>    12
> 9               a               5               2               5
>     6
> 12              b               8               6               8
>     9
>
>
> What I would like to do is:
> **To create new variables with the distances from every patient to every
> possible hospital in the data. So, I would like 3 new columns which will
> contain the distance from each patient to each hospital in the data.
> **Also, I would like to have those new columns labeled dist_a, dist_b and
> dist_c.
>
> Is there an efficient way to achieve this?
> In the real data, I have many more patients and hospitals (hundreds in fact)
> so I would like to generate these variables in an as automated way as
> possible.
>
> Any help is appreciated.
> Thanks!
> Ana
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> *
> *   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/
>



-- 
Dr. Yuval Arbel
School of Business
Carmel Academic Center
4 Shaar Palmer Street, Haifa, Israel
e-mail: yuval.arbel@gmail.com

*
*   For searches and help try:
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