From: mail@...
Date: 2014-10-08T04:33:44+00:00
Subject: [ruby-core:65510] [ruby-trunk - Feature #10077] [PATCH] Implement Matrix#row_merge and Matrix#column_merge

Issue #10077 has been updated by gogo tanaka.


@Marc-Andre Lafortune san

It���s hard for me to say this, but I have confidence in my implementation more than merged one.

My implementation

```
def row_merge(*matrices)
  if matrices.any?{|m| m.row_size != row_size}
    raise ErrDimensionMismatch, "all matrices should have same row size"
  end
  transpose.column_merge(*matrices.map(&:transpose)).transpose
end
alias_method :merge, :row_merge

def column_merge(*matrices)
  if matrices.any?{|m| m.column_size != column_size }
    raise ErrDimensionMismatch, "all matrices should have same column size"
  end
  new_matrix [self, *matrices].map(&:to_a).flatten(1)
end
```

Merged implementation

```
def Matrix.hstack(x, *matrices)
  raise TypeError, "Expected a Matrix, got a #{x.class}" unless x.is_a?(Matrix)
  result = x.send(:rows).map(&:dup)
  total_column_count = x.column_count
  matrices.each do |m|
    raise TypeError, "Expected a Matrix, got a #{m.class}" unless m.is_a?(Matrix)
    if m.row_count != x.row_count
      raise ErrDimensionMismatch, "The given matrices must have #{x.row_count} rows, but one has #{m.row_count}"
    end
    result.each_with_index do |row, i|
      row.concat m.send(:rows)[i]
    end
    total_column_count += m.column_count
  end
  new result, total_column_count
end



def Matrix.vstack(x, *matrices)
  raise TypeError, "Expected a Matrix, got a #{x.class}" unless x.is_a?(Matrix)
  result = x.send(:rows).map(&:dup)
  matrices.each do |m|
    raise TypeError, "Expected a Matrix, got a #{m.class}" unless m.is_a?(Matrix)
    if m.column_count != x.column_count
      raise ErrDimensionMismatch, "The given matrices must have #{x.column_count} columns, but one has #{m.column_count}"
    end
    result.concat(m.send(:rows))
  end
  new result, x.column_count
end
```

I believe the interface `x.row_merge(y) is preferred to Matrix.vstack(x, y)`,

And I think my implementation is more clear and maintainability.

Of course, merged one has some better point my patch doesn't have.

But we should use symmetry between row and column at least.

How is merged implementation preferred to my implementation?


I'm so sorry, I said something trouble.

Take you time.

----------------------------------------
Feature #10077: [PATCH] Implement Matrix#row_merge and Matrix#column_merge
https://bugs.ruby-lang.org/issues/10077#change-49285

* Author: gogo tanaka
* Status: Closed
* Priority: Normal
* Assignee: Marc-Andre Lafortune
* Category: lib
* Target version: 
----------------------------------------
Merge matrices horizontally  and vertically.

It is useful and important when we handle linear equations, statistics and so on.


```
Matrix[[1, 2], [3, 4]].row_merge(Matrix[[5], [6]])

  => 1 2 5
     3 4 6

Matrix[[1, 2], [3, 4]].column_merge(Matrix[[5, 6]])

  => 1 2
     3 4
     5 6

# accept more than two matrices as an argument.

Matrix[[1, 2], [3, 4]].column_merge(Matrix[[5, 6]], Matrix[[7, 8]])

  => 1 2
     3 4
     5 6
     7 8
```

* Matrix#row_merge needs Matrix#column

---Files--------------------------------
Implement_Matrix#column_merge.patch (863 Bytes)
Add_test_for_Matrix#column_merge.patch (1.36 KB)
Add_Matrix#column_merge_to_NEWS.patch (452 Bytes)
Implement_Matrix#row_merge.patch (899 Bytes)
Add_test_for_Matrix#row_merge.patch (1.4 KB)
Add_Matrix#row_merge_to_NEWS.patch (523 Bytes)


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