## Gas cost difference between uint[] and mapping(uint => uint)

When mapping for example a large integer to some integer,

``````uint[] index;
index.length = 1000000;
index[600001] = 4;
``````

is it cheaper to use

``````mapping(uint => uint) index;
index[600001] = 4;
``````

? one benefit of using `uint[]` is that it can be deleted, happens to be useful in a dApp I work on.

## Do I use actual data or data difference to train machine learning model?

I would like to predict tomorrows temperature :-).

But I’m unsure of the best approach. Do I simply drop data from the last x days, or do I try do drop data from the last x days in difference?

Last three days could look like: 21.3C, 22C, 21.9C

Where the difference is whatever previous, 0.7C, -0.1C

You would need more than 3 days, I’m just setting an data example. I think I also would need to insert season among other variables to complete the experiment. But I’m just asking for temperature here.

Have anyone checked this? While the temperature can be anything from -20 to 40 C with decimals (1, 0.x) makes up a lot of numbers! But with difference the range is maybe -5C to +5C, also with decimals (1, 0.x) but it beats the other range making the range smaller and therefor easier for ML to predict?

If difference is best, should I also do percentage difference since then I would take to account different climate has different swings?

## What Is the Difference Between Apparating and Disapparating?

What is the difference between Apparating and Disapparating? Are there specific circumstances wherein it would be called Apparition versus Disapparition, and vice versa?

Calling it Apparition and Disapparation when coming from Point A to Point B, and then going right back to Point A somewhat makes sense to me, because it implies a straightforward arrival and return loop. However, if a witch or wizard Apparates from his/her home to the Ministry, then continues on to Diagon Alley for some shopping, then stops by a friend’s for a visit, and then returns home, to me this implies going forwards in succession. This seems like a different kind of loop: Point A, to B, to C, to D, and then back to A. It’s not a direct arrival/return from Point A and B.

I haven’t been able to discern any pattern to when JKR uses Apparition versus Disapparition in canon — it seems random to me. Can anyone clarify the difference between the two using canon/JKR references?

## Is there any difference in the voltage and current distribution for a half wave dipole fed in the middle, or…

Is there any difference in the voltage (potential difference wrt center) and current (rate of flow of electrons) distribution for a half wave dipole fed in the middle (dipole cut in the middle,) or fed with a gamma match (dipole one piece) ?

## What is the difference between SRT and RTP?

I am trying to understand the benefits of SRT over other protocols like RTP. Haivision has a decent introductory explanation for SRT as well as a white paper, but I am unclear how it compares to RTP. There is even a github issue about using RTP with SRT. Don’t RTP and SRT address the same problem? Why would you use one over the other (or both together)?
I found a white paper discussing RTP vs MPEG-TS, it’d be helpful if there were a similar comparison made with SRT.