Package com.macrofocus.high_d.parallelcoordinates.geometry.curve

Class GroupIterator

  • public class GroupIterator
extends java.lang.Object

    A GroupIterator allows a curve to choose the points from a control-path that the curve uses to define itself. The subset of points to use is defined by a control-string. The control-string is evaluated to produce a series of integer groups that are iterated over.

    A common way to create a GroupIterator that uses all the points of a control-path is: 

     GroupIterator gi = new GroupIterator("0:n-1", cp.getNumPoints());

    The "0:n-1" is the control-string and cp is a control-path. Once created, the groups that are iterated over cannot be changed. Thus, if the number of points in the control-path changes, then a new group iterator is required.

    Some blended curves do not evaluate over the first and last points. A technique to get the curve to connect to the endpoints is to create duplicate endpoints. But instead of doing that, a control-string such as "0,0:n-1,n-1" will do the same thing.

    The syntax of the control-string is fairly basic. A control-string consists of one or more groups separated by a comma and possibly additional whitespace. Each group consists of either 1 or 2 expressions. If there are two expressions, then a colon ':' separates them. The expressions are parsed using the ExpressionTree.parse(String) method. Each expression can contain at most one variable and the value of that variable is set to the value specified in the GroupIterator constructor. An exception is thrown if there are multiple variables in a single expression. The result of evaluating the expressions is rounded.

    Detailed Example

    Suppose the control-string is: "1:4,8:n/2,7:3,5"
    Suppose n = 21, then the internal group array is {1, 4, 8, 11, 7, 3, 5, 5}
    Notice that the length of the group array is twice the number groups.
    The group size is (|1 - 4| + 1) + (|8 - 11| + 1) + (|7 - 3| + 1) + (|5 - 5| + 1) = 14. 

     GroupIterator gi = new GroupIterator("1:4,8:n/2,7:3,5", 21);

 while (gi.hasNext())
 System.out.print(gi.next() + ", ");

 Output:  1, 2, 3, 4, 8, 9, 10, 11, 7, 6, 5, 4, 3, 5
 index_i: 0, 0, 0, 0, 2, 2,  2,  2, 4, 4, 4, 4, 4, 6
 count_j: 0, 1, 2, 3, 0, 1,  2,  3, 0, 1, 2, 3, 4, 0

    Notice that the number of numbers outputted is 14, which is the group size. At this point, calling next() will result in an exception. However, GroupIterator objects are reusable and can be reset by calling the reset() method or by calling set(0, 0).

    The variables index_i and count_j represent the current state of the group-iterator. The index_i is an index location in the internal group-array that keeps track of the current group. Since each group always has a start index and a finish index, index_i refers to the first index and increments by 2.

    The count_j variable increments by one until group[index_i] ± count_j == group[index_i + 1]. At this point, count_j is reset to 0 and index_i is incremented by 2.

    See Also:
    Curve, ControlPath

    • Constructor Summary

      Constructors 
      Constructor Description
      GroupIterator​(int[] group)
      Constructs a group-iterator by copying the specified group array into a new internal array.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int count_j()
      count_j is the increment that keeps track of the position in the current group.
      int getGroupSize()
      Returns the total number of times next() can be called before hasNext() returns false starting from state 0, 0.
      boolean hasNext()
      Returns true if the iterator is not finished.
      int index_i()
      index_i is the index location into the internal group array of the current group.
      boolean isInRange​(int min, int max)
      Returns true if all values returned by next() are >= min and < max, false otherwise.
      int next()
      Returns the current index and advances the state to the next index.
      void set​(int index_i, int count_j)
      Sets the current state of the iterator.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • GroupIterator

        public GroupIterator​(int[] group)
        Constructs a group-iterator by copying the specified group array into a new internal array. A control-string is created based on the values in the array.

    • Method Detail

      • getGroupSize

        public int getGroupSize()
        Returns the total number of times next() can be called before hasNext() returns false starting from state 0, 0.

      • hasNext

        public boolean hasNext()
        Returns true if the iterator is not finished. True will be returned if the value of index_i is less than the internal group array length, false otherwise.

      • next

        public int next()
        Returns the current index and advances the state to the next index.

      • set

        public void set​(int index_i,
                int count_j)
        Sets the current state of the iterator.

      • index_i

        public int index_i()
        index_i is the index location into the internal group array of the current group.

      • count_j

        public int count_j()
        count_j is the increment that keeps track of the position in the current group.

      • isInRange

        public boolean isInRange​(int min,
                         int max)
        Returns true if all values returned by next() are >= min and < max, false otherwise. This is useful to determine if next() will generate an index value outside of a specified range.