shuffle 2D array in one dimension without effecting other dimension

Question

^no. not like that. 2D. I want to shuffle one D without changing at all the other D. plus thats about android. get that outta here.

I have a 2D array which is made up of elements:

Example:

Document 1 = ["I", "am", "awesome"]
Document 2 = ["I", "am", "great", "great"]

Dictionary is:

["I", "am", "awesome", "great"]

So the 2D array would look like:

[1, 1, 1, 0]
[1, 1, 0, 2]

What I want to do is shuffle around the location of the documents, so where we once had:

Document 1 = [1, 1, 1, 0]
Document 2 = [1, 1, 0, 2]

We now might have:

Document 2 = [1, 1, 0, 2]
Document 1 = [1, 1, 1, 0]

Or we might not. It should be shuffled randomly.

Not like this.

How to implement that?

My data structure looks like this:

int z = 0;
for ( Cell< int[] , String , Integer > cell: train_freq_count_against_globo_dict.cellSet() )
{              
    int[] container_of_feature_vector = cell.getRowKey();

    // 'q' CAN'T be shuffled, 'z' MUST be shuffled.
    for (int q = 0; q < globo_dict_size; q++) 
    {
        feature_matrix__train[z][q] = container_of_feature_vector[q];
     }
    // use 1 and -1 not 0 and 1
    outputs__train[z] = String.valueOf( cell.getColumnKey() ).equals(LABEL) ? 1.0 : -1.0;

     z++;
}

The point of this is to implement stochastic gradient descent.

UPDATE:

  static double[][] shuffleArray(double[][] input_array)
  {  
    Random rnd = new Random();
    for (int i = input_array.length - 1; i > 0; i--)
    {
      int index = rnd.nextInt(i + 1);
      // Simple swap
      double[] container = input_array[index];
      input_array[index] = input_array[i];
      input_array[i] = container;
    }
    return input_array;
  }

possible duplicate of [Random shuffling of an array](http://stackoverflow.com/questions/1519736/random-shuffling-of-an-array) — Thomas Jungblut, Mar 13 '15 at 10:32
@ThomasJungblut no, not the same. i want to just shuffle the 1D without effecting the other D — smatthewenglish, Mar 13 '15 at 10:40
Yep, exactly like that. Please post that as an answer and accept it. — Thomas Jungblut, Mar 13 '15 at 11:04
@Herr Thomas, I just ran it and the F1 was sonder low, i think actually that's not the right way — smatthewenglish, Mar 13 '15 at 11:32
There is no guarantee that randomization will give you a better f1 score. — Thomas Jungblut, Mar 13 '15 at 14:09

score 0 · Accepted Answer · answered Mar 13 '15 at 11:10

Do it like this!

But don't take my word for it, use System.out.println(Arrays.deepToString(input_array)); and verify that result yourself. science.

  static double[][] shuffleArray(double[][] input_array)
  {  
    Random rnd = new Random();
    for (int i = input_array.length - 1; i > 0; i--)
    {
      int index = rnd.nextInt(i + 1);
      // Simple swap
      double[] container = input_array[index];
      input_array[index] = input_array[i];
      input_array[i] = container;
    }
    return input_array;
  }

shuffle 2D array in one dimension without effecting other dimension

1 Answers1