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# Re: st: Re: Stata matrix to Mata matrix form - Turn lower diagonal matrix

 From Nick Cox To statalist@hsphsun2.harvard.edu Subject Re: st: Re: Stata matrix to Mata matrix form - Turn lower diagonal matrix Date Thu, 1 Nov 2012 17:11:46 +0000

```I mean what is the element in row 1 and column 2 of your matrix?

mat_s2[1,2]

will display it in Mata.

I may be missing something important, but I don't understand how your
matrix can display like that unless it is symmetric.

Nick

On Thu, Nov 1, 2012 at 4:46 PM, Bianca B. <bianca268@yahoo.com> wrote:

> mat_S2[1,2] is the name of the matrix.
>
>   mat_S2
>
>    1   2
>    +---------+
>  1 |  0      |
>    |  1   0
>    |
>> >+---------+
> I found this old post
> http://www.stata.com/statalist/archive/2007-02/msg00156.html
>
> where there is exactly my same question that is to turn my lower-triangular matrix, named mat_S2, into a symmetrical matrix by reflecting the lower triangular elements across the diagonal.
>
> I tried to use mata makesymmetric function but I do not obtain the matrix I wish and that I report below
>
>          1   2
>       +---------+
>     1 |  0   1  |
>     2 |  1   0  |
>       +---------+
>
>
>
> --- On Thu, 11/1/12, Nick Cox <njcoxstata@gmail.com> wrote:
>
>> From: Nick Cox <njcoxstata@gmail.com>
>> Subject: Re: st: Re: Stata matrix to Mata matrix form
>> To: statalist@hsphsun2.harvard.edu
>> Date: Thursday, November 1, 2012, 9:34 AM
>> You've lost me. What is mat_S2[1,2]?
>>
>> Nick
>>
>> On Thu, Nov 1, 2012 at 3:39 PM, Bianca B. <bianca268@yahoo.com>
>> wrote:
>> > Nick, you're right, I'm sorry. I didn't specify that I
>> need to turn my lower-triangular matrix into a symmetrical
>> matrix by reflecting the lower triangular elements across
>> the diagonal. So starting from this matrix
>> >
>> > mat_S2
>> >
>> >
>>    1   2
>> >      +---------+
>> >    1 |  0      |
>> >    2 |  1   0
>> >      |
>> >      +---------+
>> >  I'd like to obtain a matrix like that
>> >
>> >
>>    1   2
>> >      +---------+
>> >    1 |  0   1  |
>> >    2 |  1   0  |
>> >      +---------+
>> >
>> >
>> >
>> >
>> > --- On Thu, 11/1/12, Nick Cox <njcoxstata@gmail.com>
>> wrote:
>> >
>> >> From: Nick Cox <njcoxstata@gmail.com>
>> >> Subject: Re: st: Re: Stata matrix to Mata matrix
>> form
>> >> To: statalist@hsphsun2.harvard.edu
>> >> Date: Thursday, November 1, 2012, 8:29 AM
>> >> Looks symmetric to me.
>> >>
>> >> If a matrix is symmetric, Stata says so, and only
>> displays
>> >> the lower
>> >> half (including the principal diagonal).
>> >>
>> >> In your case, Stata is doing exactly that.
>> >>
>> >> Here is another example:
>> >>
>> >> . mata : I(3)
>> >> [symmetric]
>> >>
>> >>
>> 1   2   3
>> >>     +-------------+
>> >>   1 |  1
>>     |
>> >>   2 |
>> 0   1      |
>> >>   3 |
>> >> 0   0   1  |
>> >>     +-------------+
>> >>
>> >> If this is not what you mean, you'll have to
>> explain what
>> >> "doesn't
>> >> work" means exactly.
>> >>
>> >> Nick
>> >>
>> >> On Thu, Nov 1, 2012 at 3:16 PM, Bianca B. <bianca268@yahoo.com>
>> >> wrote:
>> >> > Dear Nick,
>> >> >
>> >> > Thanks a lot. I converted a lower-triangular
>> matrix
>> >> from stata to mata form to apply the mata
>> makesymmetric
>> >> command but it doesn't work.
>> >> > The command is
>> >> >
>> >> > : makesymmetric(mat_S2)
>> >> > [symmetric]
>> >> >
>> 1   2
>> >> >     +---------+
>> >> >   1 |  0
>>   |
>> >> >   2 |
>> 1   0
>> >> |
>> >> >     +---------+
>> >> >
>> >> > Would you have any suggestion?
>> >> > Best,
>> >> > Bianca
>> >> >
>> >> >
>> >> >
>> >> > . mat foo = J(6,7,42)
>> >> >
>> >> > . mat li foo
>> >> >
>> >> > foo[6,7]
>> >> >     c1  c2  c3
>> >> c4  c5  c6  c7
>> >> > r1  42  42  42  42
>> 42
>> >> 42  42
>> >> > r2  42  42  42  42
>> 42
>> >> 42  42
>> >> > r3  42  42  42  42
>> 42
>> >> 42  42
>> >> > r4  42  42  42  42
>> 42
>> >> 42  42
>> >> > r5  42  42  42  42
>> 42
>> >> 42  42
>> >> > r6  42  42  42  42
>> 42
>> >> 42  42
>> >> >
>> >> > . mata : mat_foo = st_matrix("foo")
>> >> >
>> >> > . mata : mat_foo
>> >> >         1
>> >> 2    3    4    5
>> >> 6    7
>> >> >
>> >>
>> +------------------------------------+
>> >> >   1 |
>> >>
>> 42   42   42   42   42   42   42
>> >> |
>> >> >   2 |
>> >>
>> 42   42   42   42   42   42   42
>> >> |
>> >> >   3 |
>> >>
>> 42   42   42   42   42   42   42
>> >> |
>> >> >   4 |
>> >>
>> 42   42   42   42   42   42   42
>> >> |
>> >> >   5 |
>> >>
>> 42   42   42   42   42   42   42
>> >> |
>> >> >   6 |
>> >>
>> 42   42   42   42   42   42   42
>> >> |
>> >> >
>> >>
>> +------------------------------------+
>> >> >
>> >> > . mata : st_matrix("foo", mat_foo :/ 7)
>> >> >
>> >> > . mat li foo
>> >> >
>> >> > foo[6,7]
>> >> >     c1  c2  c3
>> >> c4  c5  c6  c7
>> >> >
>> >>
>> r1   6   6   6   6   6   6   6
>> >> >
>> >>
>> r2   6   6   6   6   6   6   6
>> >> >
>> >>
>> r3   6   6   6   6   6   6   6
>> >> >
>> >>
>> r4   6   6   6   6   6   6   6
>> >> >
>> >>
>> r5   6   6   6   6   6   6   6
>> >> >
>> >>
>> r6   6   6   6   6   6   6   6
>> >> >
>> >> > --- On Thu, 11/1/12, Bianca B. <bianca268@yahoo.com>
>> >> wrote:
>> >> >
>> >> >> From: Bianca B. <bianca268@yahoo.com>
>> >> >> Subject: Stata matrix to Mata matrix form
>> >> >> To: statalist@hsphsun2.harvard.edu
>> >> >> Date: Thursday, November 1, 2012, 7:25 AM
>> >> >> Hi Stata users,
>> >> >>
>> >> >> Does anyone know how can I get stata
>> matrix in mata
>> >> matrix?
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