• David (21/21) Dec 15 2018 Hi
• 9il (4/25) Dec 26 2018 matrix[2][] = vector;
• David (4/37) Dec 27 2018 great many thanks!! Is there any logic why getting a row works by
• 9il (12/54) Dec 28 2018 This case gets a slice of a row, it does not copy the data. So
• 9il (2/26) Dec 28 2018 EDIT: a slice on the LEFT side
• David (2/26) Dec 28 2018 Many thanks for this background!!

David <scherd3113 gmail.com> writes:

Hi

I am wondering if it is possible to assign a vector to a row of a 
matrix?

============ main.d ==========
import mir.ndslice;

void main() {

   auto matrix = slice!double(3, 4);
   matrix[] = 0;
   matrix.diagonal[] = 1;

   auto row = matrix[0];
   row[3] = 4;
   assert(matrix[0, 3] == 4);

   // assign it to rows of a matrix?
   auto vector = sliced!(double)([10, 11, 12, 13]);

   // ??? Here I would like to assign the vector to the last (but 
it is not working)
   // matrix[2] = vector;
}
============

So I am wondering what the correct way is to do such an 
assignment without looping?

9il <ilyayaroshenko gmail.com> writes:

On Saturday, 15 December 2018 at 19:04:37 UTC, David wrote:
 Hi

 I am wondering if it is possible to assign a vector to a row of 
 a matrix?

 ============ main.d ==========
 import mir.ndslice;

 void main() {

   auto matrix = slice!double(3, 4);
   matrix[] = 0;
   matrix.diagonal[] = 1;

   auto row = matrix[0];
   row[3] = 4;
   assert(matrix[0, 3] == 4);

   // assign it to rows of a matrix?
   auto vector = sliced!(double)([10, 11, 12, 13]);

   // ??? Here I would like to assign the vector to the last 
 (but it is not working)
   // matrix[2] = vector;
 }
 ============

 So I am wondering what the correct way is to do such an 
 assignment without looping?

matrix[2][] = vector;

Or

matrix[2,0..$] = vector;

David <scherd3113 gmail.com> writes:

On Wednesday, 26 December 2018 at 18:59:25 UTC, 9il wrote:
 On Saturday, 15 December 2018 at 19:04:37 UTC, David wrote:
 Hi

 I am wondering if it is possible to assign a vector to a row 
 of a matrix?

 ============ main.d ==========
 import mir.ndslice;

 void main() {

   auto matrix = slice!double(3, 4);
   matrix[] = 0;
   matrix.diagonal[] = 1;

   auto row = matrix[0];
   row[3] = 4;
   assert(matrix[0, 3] == 4);

   // assign it to rows of a matrix?
   auto vector = sliced!(double)([10, 11, 12, 13]);

   // ??? Here I would like to assign the vector to the last 
 (but it is not working)
   // matrix[2] = vector;
 }
 ============

 So I am wondering what the correct way is to do such an 
 assignment without looping?

 matrix[2][] = vector;

 Or

 matrix[2,0..$] = vector;

great many thanks!! Is there any logic why getting a row works by

auto row = matrix[0];

but assigning to a row works (only) by the two variant you posted?

9il <ilyayaroshenko gmail.com> writes:

On Thursday, 27 December 2018 at 21:17:48 UTC, David wrote:
 On Wednesday, 26 December 2018 at 18:59:25 UTC, 9il wrote:
 On Saturday, 15 December 2018 at 19:04:37 UTC, David wrote:
 Hi

 I am wondering if it is possible to assign a vector to a row 
 of a matrix?

 ============ main.d ==========
 import mir.ndslice;

 void main() {

   auto matrix = slice!double(3, 4);
   matrix[] = 0;
   matrix.diagonal[] = 1;

   auto row = matrix[0];
   row[3] = 4;
   assert(matrix[0, 3] == 4);

   // assign it to rows of a matrix?
   auto vector = sliced!(double)([10, 11, 12, 13]);

   // ??? Here I would like to assign the vector to the last 
 (but it is not working)
   // matrix[2] = vector;
 }
 ============

 So I am wondering what the correct way is to do such an 
 assignment without looping?

 matrix[2][] = vector;

 Or

 matrix[2,0..$] = vector;

 great many thanks!! Is there any logic why getting a row works 
 by

 auto row = matrix[0];

 but assigning to a row works (only) by the two variant you 
 posted?

This case gets a slice of a row, it does not copy the data. So 
row[i] is matrix[0, i], the same number in the RAM.

auto row = matrix[0];

This case gets a slice of a row, it does not copy the data.

If you wish to copy data you need to use a slice on the right 
side:

row[] = matrix[0];

or

auto row = matrix[0].slice; // 'slice' allocates new data

For columns:

col[] = matrix[0 .. $, 0];

9il <ilyayaroshenko gmail.com> writes:

On Friday, 28 December 2018 at 08:09:09 UTC, 9il wrote:
 On Thursday, 27 December 2018 at 21:17:48 UTC, David wrote:
 On Wednesday, 26 December 2018 at 18:59:25 UTC, 9il wrote:
 On Saturday, 15 December 2018 at 19:04:37 UTC, David wrote:
 [...]

 matrix[2][] = vector;

 Or

 matrix[2,0..$] = vector;

 great many thanks!! Is there any logic why getting a row works 
 by

 auto row = matrix[0];

 but assigning to a row works (only) by the two variant you 
 posted?

 This case gets a slice of a row, it does not copy the data. So 
 row[i] is matrix[0, i], the same number in the RAM.

 auto row = matrix[0];

 This case gets a slice of a row, it does not copy the data.

 If you wish to copy data you need to use a slice on the right 
 side:

EDIT: a slice on the LEFT side

David <scherd3113 gmail.com> writes:

On Friday, 28 December 2018 at 08:11:37 UTC, 9il wrote:
 On Friday, 28 December 2018 at 08:09:09 UTC, 9il wrote:
 On Thursday, 27 December 2018 at 21:17:48 UTC, David wrote:
 On Wednesday, 26 December 2018 at 18:59:25 UTC, 9il wrote:
 [...]

 great many thanks!! Is there any logic why getting a row 
 works by

 auto row = matrix[0];

 but assigning to a row works (only) by the two variant you 
 posted?

 This case gets a slice of a row, it does not copy the data. So 
 row[i] is matrix[0, i], the same number in the RAM.

 auto row = matrix[0];

 This case gets a slice of a row, it does not copy the data.

 If you wish to copy data you need to use a slice on the right 
 side:

 EDIT: a slice on the LEFT side

Many thanks for this background!!