I'd like to kick-up this thread again, and ask a related questions:
Let's say I have a 2d array, and take a slice of it. How do I then append
the slice with an additional value? The slice is type Array{Float64,2}.
Neither push! or append! work.
Thanks,
Alex
On Wednesday, April 16, 2014 at 5:25:36 PM UTC-5, Paweł Biernat wrote:
>
> Thanks for linking to the issue. It seems that the array slicing is just
> a tip of the iceberg, I had no idea about the discussion on the algebraic
> interpretation of n x n arrays and respective operators. I somewhat
> understand the arguments behind the need of elementwise operators (although
> they are still pretty arbitrary), but I find the current state of array
> slicing really unintuitive. I am new to Julia and I am constantly
> impressed by its features but for my work a decent array slicing rules are
> critical and lack of them is, to me, very annoying.
>
> W dniu środa, 16 kwietnia 2014 20:54:59 UTC+2 użytkownik Bob Nnamtrop
> napisał:
>>
>> I completely agree with you and would love to see julia drop singleton
>> dimensions indexed with scalar. There is an issue on this with lots of
>> discussion, which was left at the point of waiting til someone implements
>> some code to give it a try (see
>> https://github.com/JuliaLang/julia/issues/5949). Maybe after 0.3 is
>> released there will be some action on this (I am willing to try myself but
>> it does seem like a hard 1st problem to deal with the julia internals).
>> IMO, there is some underlying tension in julia that revolves around people
>> who primarily use arrays as containers (who generally want this changed)
>> and those who use one and two dimensional arrays as a linear algebra system
>> (some of who do not want it implemented). I am firmly in the camp of using
>> arrays primarily as containers and, in addition to this issue, find it very
>> annoying that the elementwise operators are all are 2nd class citizens
>> (i.e., you must use .*, ./, .+, .-, etc). The fact that the 1st class
>> versions only work on a subset of arrays (i.e., those 1 and 2 dimensional)
>> seems like a poor design choice to me. But this is different to the
>> dripping dimensions indexed by scalars issue where there is still hope for
>> a change.
>>
>> As a practical version of your function example in your second email is
>> the plot command. You are plotting some slices from some higher dimensional
>> arrays, e.g.
>>
>> plot(x[2,3,7,:,9], y[2,3,7,:,9])
>>
>> and you just want to get two one dimensional slices passed into plot with
>> no fuss.
>>
>> Bob
>>
>>
>> On Wed, Apr 16, 2014 at 12:13 PM, Paweł Biernat <pawel....@gmail.com>
>> wrote:
>>
>>> Adding a real life use case:
>>>
>>> x=[j+10*i for i=1:2, j=1:2]
>>>
>>> function f(x::Array{Int,1})
>>> x
>>> end
>>>
>>> and then
>>>
>>> julia> f(x[1:2,1])
>>>
>>> 2-element Array{Int64,1}:
>>> 11
>>> 21
>>>
>>>
>>> julia> f(x[1,1:2])
>>> ERROR: no method f(Array{Int64,2})
>>>
>>>
>>>
>>
