dividing an array into 3 individual arrays

Question

I have 45 values stored in an array, sample. It needs to be split into three individual arrays of size 15, sample1, sample2 and sample3: the first 15 items into sample1, the next 15 into sample2 and the remaining 15 into sample3. I tried to do that with this code:

var
  sample: array of integer; // Source Array which contains data
  sample1, sample2, sample3: array of integer; //Target arrays which needs to be worked upon
  i: integer;
begin
 SetLength(sample1, 15);
 SetLength(sample2, 15);
 SetLength(sample3, 15); 
 for i := 0 to 14 do
   sample[i] := sample1[i];
 for i:= 15 to 29 do
   sample[i] := sample2[i];  
 for i:= 30 to 44 do
   sample[i] := sample3[i];
 i := i + 1;

I am able to get the results in the first array, but not in the other arrays. What am I doing wrong?

Answer 1

If I understand you well, the following is what you want. I assume your sample array has exactly 45 items, so you probably want to do this:

var 
  sample: array of Integer;
  sample1, sample2, sample3: array of Integer;
  i: Integer;
begin
  SetLength(sample, 45);
  { fill sample with values }
  ...
  { now split: }
  SetLength(sample1, 15);
  SetLength(sample2, 15);
  SetLength(sample3, 15);
  for i := 0 to 14 do
  begin
    sample1[i] := sample[i];
    sample2[i] := sample[i + 15]; { i = 0..14, so i+15 = 15..29 }
    sample3[i] := sample[i + 30]; { i = 0..14, so i+30 = 30..44 } 
  end;

That should do the trick. If this is not what you wanted, then you should specify your problem a bit better. If you sample array is longer, this won't split all of it. If your sample array is shorter, you'll get an overflow, causing an error or undefined behaviour.