# Silly question. How to add a row to array?

**URL:** <https://discourse.julialang.org/t/silly-question-how-to-add-a-row-to-array/33601>\
**Category:** New to Julia\
**Tags:** array\
**Created:** [January 20, 2020, 9:49pm UTC](https://discourse.julialang.org/t/silly-question-how-to-add-a-row-to-array/33601 "2020-01-20T21:49:00Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![Jakub\_Wronowski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jakub_wronowski/32/204030_2.png) [@Jakub\_Wronowski](https://discourse.julialang.org/u/Jakub_Wronowski)\
**Post date:** [January 20, 2020, 10:14pm UTC](https://discourse.julialang.org/t/silly-question-how-to-add-a-row-to-array/33601/6 "2020-01-20T22:14:52Z")

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I really understand your pain:

> [@Concatenating iterables without allocating memory](https://discourse.julialang.org/t/concatenating-iterables-without-allocating-memory/33282):
>
> Hi, for a library I am working now I need to find minimum and maximum values. I am looking elegant way to express that. signal1 = rand(10000000) signal2 = rand(10000000) @time lo, hi = extrema(vcat(signal1, signal2)) 0.159702 seconds (7 allocations: 152.588 MiB) Code above looks good but allocates lots of memory just to iterate values, so it’s not making sense for me. In C# I can write (lo, hi) = signal1.Concat(signal2).Extrema(); and there is no allocation at all. It there any predefined…

> <https://github.com/JuliaLang/julia/issues/34385>
>
> Hi,
> 
> The issue I am reporting is related to discourse conversation: https://di…scourse.julialang.org/t/concatenating-iterables-without-allocating-memory/33282
> Also I commented some details to other issue: https://github.com/JuliaLang/julia/issues/31442#issuecomment-573939429
> 
> I encountered it using \`extrema\` function with flattened iterator, but here I am providing more distilled example.
> 
> First of all I need 2 big arrays which we are going to concatenate with a lazy iterator.
> \`\`\`
> const signal1 = rand(10000000)
> const signal2 = rand(10000000)
> const flat = Iterators.flatten((signal1, signal2))
> \`\`\`
> 
> Now I am going to define a functions that will iterate this flattened data. They are based on \`extrema\` implementation.
> 
> \`\`\` julia
> function works\_ok(itr)
> y = iterate(itr)
> (v, s) = y
> y = iterate(itr, s)
> while y !== nothing
> (v, s) = y
> y = iterate(itr, s)
> end
> 
> return v
> end
> 
> function gives\_strange\_result(itr)
> y = iterate(itr)
> (v, s) = y
> while y !== nothing
> y = iterate(itr, s)
> y === nothing && break
> (v, s) = y
> end
> 
> return v
> end
> \`\`\`
> 
> The second one has strange timings and memory consumption.
> 
> \`\`\`
> julia\> @time works\_ok(flat)
> 0.024651 seconds (7 allocations: 240 bytes)
> 0.9342115147070622
> 
> julia\> @time gives\_strange\_result(flat)
> 0.252765 seconds (20.00 M allocations: 610.352 MiB, 22.57% gc time)
> 0.9342115147070622
> \`\`\`
> 
> There is no memory leak, I tried to run in a loop 1000 times.

If you need to add new row and still have Array, not lazy iterator, you need to move data to make place for this new bytes. Allocating new array may be perfect, just copy data, and GC will free old one.

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