I filed https://github.com/JuliaLang/julia/issues/6676
-viral
On Monday, April 28, 2014 4:04:33 AM UTC+5:30, Simon Kornblith wrote:
>
> If diag is passed a vector rather than a matrix, we already give a good
> error message:
>
> julia> diag([1, 2, 3, 4])
> ERROR: use diagm instead of diag to construct a diagonal matrix
> in diag at linalg/generic.jl:49
>
> It wouldn't hurt to have this in the docs, though.
>
> On Sunday, April 27, 2014 4:07:52 PM UTC-4, Andreas Noack Jensen wrote:
>>
>> I agree. It would probably avoid some confusion if the documentation was
>> a little longer and pointed to diagm and Diagonal.
>>
>>
>> 2014-04-27 22:02 GMT+02:00 Ivar Nesje <iva...@gmail.com>:
>>
>>> This difference should be explained in the documentation for diag
>>>
>>> The current documentation is kind of short:
>>>
>>> Base.diag(M[, k])
>>> The "k"-th diagonal of a matrix, as a vector.
>>>
>>> Ivar
>>>
>>> kl. 21:54:43 UTC+2 søndag 27. april 2014 skrev John Code følgende:
>>>
>>>> Thank you.
>>>>
>>>> On Sunday, April 27, 2014 11:49:12 PM UTC+4, Andreas Noack Jensen wrote:
>>>>>
>>>>> Hi John
>>>>>
>>>>> In julia, the function diag extract the diagonal of a matrix and if
>>>>> the matrix is rectangular, it extracts the diagonal of the largest square
>>>>> sub matrix. Note that in julia, [1 2 3 4] is not vector but a matrix. To
>>>>> construct a matrix from a vector you can either use the function diagm,
>>>>> which does what you expected diag did,
>>>>>
>>>>> julia> diagm([1,2,3,4])
>>>>> 4x4 Array{Int64,2}:
>>>>> 1 0 0 0
>>>>> 0 2 0 0
>>>>> 0 0 3 0
>>>>> 0 0 0 4
>>>>>
>>>>> but it is often better to use Diagonal, which creates a special
>>>>> Diagonal matrix,
>>>>>
>>>>> julia> Diagonal([1,2,3,4])
>>>>>
>>>>> 4x4 Diagonal{Int64}:
>>>>> 1 0 0 0
>>>>> 0 2 0 0
>>>>> 0 0 3 0
>>>>> 0 0 0 4
>>>>>
>>>>>
>>>>> 2014-04-27 21:40 GMT+02:00 John Code <jcod...@gmail.com>:
>>>>> >
>>>>> > Hi all,
>>>>> > I would like to ask why there is a difference between Octave diag
>>>>> function
>>>>> > and the function that julia provide. For example, in the following
>>>>> Octave session I get:
>>>>> >
>>>>> > ============================
>>>>> > octave:1> v = [1 2 3 4]
>>>>> > v =
>>>>> >
>>>>> > 1 2 3 4
>>>>> >
>>>>> > octave:2> a = diag(v)
>>>>> > a =
>>>>> >
>>>>> > Diagonal Matrix
>>>>> >
>>>>> > 1 0 0 0
>>>>> > 0 2 0 0
>>>>> > 0 0 3 0
>>>>> > 0 0 0 4
>>>>> > =============================
>>>>> >
>>>>> > But in Julia I get:
>>>>> >
>>>>> > =============================
>>>>> > julia> v = [1 2 3 4]
>>>>> > 1x4 Array{Int64,2}:
>>>>> > 1 2 3 4
>>>>> >
>>>>> > julia> a = diag(v)
>>>>> > 1-element Array{Int64,1}:
>>>>> > 1
>>>>> >
>>>>> >
>>>>> > =============================
>>>>> >
>>>>> >
>>>>> > Why is this the case and how to get a similar effect of the octave
>>>>> code.
>>>>> > Thank you.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Med venlig hilsen
>>>>>
>>>>> Andreas Noack Jensen
>>>>>
>>>>
>>
>>
>> --
>> Med venlig hilsen
>>
>> Andreas Noack Jensen
>>
>
