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Re: st: RE: mata: columns of different eltypes in a transmorphic matrix


From   László Sándor <sandorl@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: mata: columns of different eltypes in a transmorphic matrix
Date   Thu, 10 Oct 2013 14:04:23 -0400

Excellent answers, thanks a lot.

If only I could code as fast as Joseph can.

To be clear: I made an elementary mistake, I completely overlooked I
need to use st_sdata and st_sview.

Thanks again!

On Thu, Oct 10, 2013 at 8:42 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> Naturally, you do often need to combine numeric and string, and the
> answer is that strings can include numeric characters, but not vice
> versa. So, we can do things like this:
>
> sysuse auto
>
> In Mata:
>
> : make = st_sdata(., "make", "foreign")
>
> : make
>                      1
>      +------------------+
>    1 |       Audi 5000  |
>    2 |        Audi Fox  |
>    3 |        BMW 320i  |
>    4 |      Datsun 200  |
>    5 |      Datsun 210  |
>    6 |      Datsun 510  |
>    7 |      Datsun 810  |
>    8 |     Fiat Strada  |
>    9 |    Honda Accord  |
>   10 |     Honda Civic  |
>   11 |       Mazda GLC  |
>   12 |     Peugeot 604  |
>   13 |  Renault Le Car  |
>   14 |          Subaru  |
>   15 |   Toyota Celica  |
>   16 |  Toyota Corolla  |
>   17 |   Toyota Corona  |
>   18 |       VW Dasher  |
>   19 |       VW Diesel  |
>   20 |       VW Rabbit  |
>   21 |     VW Scirocco  |
>   22 |       Volvo 260  |
>      +------------------+
>
> : price  = st_data(., "price", "foreign")
>
> : make, strofreal(price, "%2.0f")
>                      1                2
>      +-----------------------------------+
>    1 |       Audi 5000             9690  |
>    2 |        Audi Fox             6295  |
>    3 |        BMW 320i             9735  |
>    4 |      Datsun 200             6229  |
>    5 |      Datsun 210             4589  |
>    6 |      Datsun 510             5079  |
>    7 |      Datsun 810             8129  |
>    8 |     Fiat Strada             4296  |
>    9 |    Honda Accord             5799  |
>   10 |     Honda Civic             4499  |
>   11 |       Mazda GLC             3995  |
>   12 |     Peugeot 604            12990  |
>   13 |  Renault Le Car             3895  |
>   14 |          Subaru             3798  |
>   15 |   Toyota Celica             5899  |
>   16 |  Toyota Corolla             3748  |
>   17 |   Toyota Corona             5719  |
>   18 |       VW Dasher             7140  |
>   19 |       VW Diesel             5397  |
>   20 |       VW Rabbit             4697  |
>   21 |     VW Scirocco             6850  |
>   22 |       Volvo 260            11995  |
>      +-----------------------------------+
> Nick
> njcoxstata@gmail.com
>
>
> On 10 October 2013 13:27, Joseph Coveney <stajc2@gmail.com> wrote:
>> Nick Cox wrote:
>>
>> This is an excellent answer, but one simple point seems submerged. An
>> elementary strategy is to put numeric variables in a numeric matrix
>> and string variables in a string matrix.  I've often done that in Mata
>> programs, and never yet felt the need for structs, pointers, and so
>> forth.
>>
>> --------------------------------------------------------------------------------
>>
>> I agree.   I'm not sure what László's needs are for keeping Stata dataset string
>> and numeric data in sync in a single location in Mata.  Perhaps, if he'd like to
>> elaborate, someone on the list could offer suggestions that don't entail structs
>> or pointer vectors, List or Array classes, and the like.
>>
>> As you could see from my example, taking the long way round involves additional
>> programming steps that in turn give rise to opportunities for logical errors,
>> such as -select(X, missing(X[1,]))- instead of -select(X, !missing(X[1,]))-, and
>> syntax errors, such as -PointerVector = (A, B)- instead of -PointerVector = &A,
>> &B-, among others that I haven't noticed yet.
>>
>> Joseph Coveney
>>
>>
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