Formula explain

[turkalturk]

Moderator note: CAN SOMEONE EXPLAIN THIS FORMULA AND ITS RESULT (( avoid shouting ))
Can Someone Explain This Formula And Its Result
=REDUCE(0,H7:H10,LAMBDA(a,b,VSTACK(TAKE(a,1),a+b)))
column H
1
2
3
4

and result is
0
4
7
9
10

Kindly explain

 

[Peter Bartholomew]

Firstly TAKE(a,1) is always 0. If one concentrates on the first difference of the sequence at each reduce step, one sees that adding a scalar b to the array a leaves differences unaltered. The new sequence starts with b and then has the 0 inserted, creating a difference of b.

At the next step the value has increased by 1, so the differences form a decreasing series and the second differences are -1. The quadratic curve this maps out terminates when the maximum value is attained.

 

[AliGW]

If you don't want the 0 result, use this:

=DROP(REDUCE(0,H7:H10,LAMBDA(a,b,VSTACK(TAKE(a,1),a+b))),1)

 

[turkalturk]

Thanks for your explanation I just want to know why range b values
pick last to first like 4,3,2,1

 

[Peter Bartholomew]

That's because at every step a 0 is inserted at the top of the list, so dropping prior calculations to the bottom.

 

[turkalturk]

thanks for your time
and if i want to calculate top to bottom