sum of array by specific index value

hi, i have two array. First array containing index and second array (hasil_tambah_array) containing the value to be sum-up as below:

index =

     4
     2
     4
     
 hasil_tambah_array =
    3.6881
    0.8506
    0.0132
    0.8506
   10.5147
   12.5147
   14.5074
   21.8003
   11.2145
   18.5074

I try to sum the second array as per index such as 3.6881,0.8506,0.0132 and 0.8506 (since the 1st index is 4) will be sum together . Then 10.5147 and 12.5147 (since the 2nd index is 2) will be sum up and respectively (next will be the rest since the index is 4).

Appreciate ur time to solve this. TQIA.

Answer 1

[DGM]

This is one way. It's probably not the most efficient way, but it does the job.

idx = [4 2 4];
H = [3.6881 0.8506 0.0132 0.8506 10.5147 12.5147 14.5074 21.8003 11.2145 18.5074].';

S = cellfun(@sum,mat2cell(H,idx,1))

S = 3×1

5.4025 23.0294 66.0296

Bear in mind that using mat2cell() to subdivide the main vector requires that sum(idx) = numel(H), so watch out for that.

[Khairul Nur]

mat2cell working great! TQ!

Answer 2

[KALYAN ACHARJYA]

result=sum(second_arary(first_array))

More

result=sum(hasil_tambah_array(index))

[Khairul Nur]

tq for replying..tried this, but the output is wrong:

result =

   11.2145

[KALYAN ACHARJYA]

index =[4
     2
     4];
hasil_tambah_array =[3.6881
    0.8506
    0.0132
    0.8506
   10.5147
   12.5147
   14.5074
   21.8003
   11.2145
   18.5074];
result=sum(hasil_tambah_array(index))

Output:

result =
    2.5518

More: Same as

>> 0.8506+0.8506+0.8506
ans =
    2.5518