CODEWITHSUNDEEP
c#multidimensional-array
blooop
blooop

Reputation: 409

Copy subsection of a multidimensional array

In Processing (java based language) I can do this;

int [][] a = new int[3][2];
for (int i = 0; i < 3; i++)
{
  a[i][0] = i;
  a[i][1] = i+3;
}
int [] b = a[2];

b is a one dimensional array with the values 2 and 5. It takes the array in row 2 of array a.

matlab syntax would be

b = a(3,:);

Is there any equivalent for c#? I can't seem to find anything but seems like a fairly useful and obvious feature.

Thanks

Upvotes: 2

Views: 2095

Answers (3)

Jon
Jon

Reputation: 437366

C# has multidimensional arrays, but it also has arrays of arrays (also called jagged arrays). The second form is what you are after:

// This is a jagged array. It has 3 rows, each of which is an int[] in its own right.
// Each row can also have a different number of elements from all the others, so if
// a[i][N] is valid for some i and N, a[x][N] is not necessarily valid for other x != i
var a = new int[3][];

// To populate the array you need to explicitly create an instance for each sub-array
for (int i = 0; i < 3; i++)
{
      a[i] = new[] { i, i + 3 };
}

// And now this is possible:
var b = a[2];

If you have a multidimensional array at hand, you will need to do the copying manually.

Upvotes: 3

Henrik
Henrik

Reputation: 23324

In addition to the other answers: if you really want a copy, i.e. you don't want b[0] = 42; to change a[2][0];, then do this:

int [] b = (int[])a[2].Clone();

Upvotes: 1

O. R. Mapper
O. R. Mapper

Reputation: 20732

C# distinguishes between jagged arrays ([][]) and multidimensional arrays ([,]):

Jagged Arrays:

This should be possible; every array element is just an array itself.

Multidimensional Arrays:

Here, you will have to do the copying yourself, element by element.

Upvotes: 1

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