Subsetting Data Series

Some specific utilities are provided for simple operations on sequences.

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void get_subsequence(Sequence& seq,int start=0, int num=-1 )
On return, seq contains a subsequence of num elements, starting from the index start. The default start index is 0, while if the number of elements to return is set to -1 (the default) the remainder of the sequence starting at index start is returned.

  #include "Qdos.h"
  QdRMatrixSeq_var ms = QdRMatrixSeq::narrow(ts_in);
  QdRMatrixSeq_var sub_seq = new QdRMatrixSeq();
    // get first 10 elements of sequence...
  ms->get_subsequence(sub_seq,0,10);
    // sub_seq contains 10 QdRMatrix objects starting from ms[0]

Note that in the above example we initialise the matrix sequence to be empty. A more efficient use of memory would be achieved if we had created it with the required number of elements and matrices of the correct dimensions, e.g.
QdRMatrixSeq_var sub_seq = new QdRMatrixSeq(10,(ms[0]).dimdata());
See Matrix Sequences below for details of this constructor.

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QdTimeSeq_var get_timetags_inrange(QdTimeSeq_var& ts_in,
QdTimeInterval_var& tint)
Constructs and returns a subsequence of the time tags object that is delimited by the specified time interval.

  #include "qplug_if.h"
  #include "Qdos.h"
  #include "QsasUtils.h"
  using namespace QSAS;
   QdObject_var input1 = (* object_list)[1]; 
   QdObject_var input2 = (* object_list)[2]; 
   QdTimeInterval_var ti = get_timeinterval(input1);
   QdTimeSeq_var tt = get_timetags(input2);
   // subset time tags on interval set in input slot 1.
   QdTimeSeq_var tt_subset = get_timetags_inrange(tt, ti);

Note this utility returns the time-tags subset, it does not subset the data series associated (see sequence mask methods below).(A)

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int get_num_timetags_inrange(QdTimeSeq_var& ts,
QdTimeInterval_var& tint)
This works as for the method above, but returns the number of time tags that lie in the requested range rather than the tags themselves. int n = get_num_timetags_inrange(ts,ti) See also sequence masks below. (A)