digitalmars.D.learn - Linear array to matrix

Giovanni Di Maria (16/16) Apr 04 2020 Hi.

Boris Carvajal (11/27) Apr 04 2020 If you're really sure about the array and matrix dimensions/types.

Giovanni Di Maria (3/39) Apr 04 2020 Ok. Thank you for your help

MoonlightSentinel (15/17) Apr 04 2020 You can combine slide [1] and array [2]:

Giovanni Di Maria (4/22) Apr 04 2020 Thank you very much.

9il (25/41) Apr 04 2020 You may want to look into a mir-algorithm package that supports

Giovanni Di Maria (4/10) Apr 04 2020 Very good.

p.shkadzko (14/30) Apr 05 2020 Why not use "chunks" from std.range?

p.shkadzko (4/19) Apr 05 2020 it should be just one call to chunks --> arr.chunks(3), otherwise

Giovanni Di Maria <calimero22 yahoo.it> writes:

Hi.
Is there a Built-in function (no code, only a built-in function)
that transform a linear array to a Matrix?

For example:

From

[10,20,30,40,50,60,70,80,90,100,110,120];


To

[
[10,20,30],
[40,50,60],
[70,80,90],
[100,110,120]
];

Thank You very much
Cheers.
Giovanni

Apr 04 2020

Boris Carvajal <boris2.9 gmail.com> writes:

On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
wrote:
 Hi.
 Is there a Built-in function (no code, only a built-in function)
 that transform a linear array to a Matrix?

 For example:

 From

 [10,20,30,40,50,60,70,80,90,100,110,120];


 To

 [
 [10,20,30],
 [40,50,60],
 [70,80,90],
 [100,110,120]
 ];

 Thank You very much
 Cheers.
 Giovanni

If you're really sure about the array and matrix dimensions/types.
You can use a cast:

     int[] a = [10,20,30,40,50,60,70,80,90,100,110,120];

     int[3][] m1 = cast(int[3][]) a;
     writeln(m1);

A better way is using the function chunks;

     import std.range;

     auto m2 = a.chunks(3);
     writeln(m2);

Apr 04 2020

Giovanni Di Maria <calimero22 yahoo.it> writes:

On Saturday, 4 April 2020 at 10:52:00 UTC, Boris Carvajal wrote:
 On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
 wrote:
 Hi.
 Is there a Built-in function (no code, only a built-in 
 function)
 that transform a linear array to a Matrix?

 For example:

 From

 [10,20,30,40,50,60,70,80,90,100,110,120];


 To

 [
 [10,20,30],
 [40,50,60],
 [70,80,90],
 [100,110,120]
 ];

 Thank You very much
 Cheers.
 Giovanni

 If you're really sure about the array and matrix 
 dimensions/types.
 You can use a cast:

     int[] a = [10,20,30,40,50,60,70,80,90,100,110,120];

     int[3][] m1 = cast(int[3][]) a;
     writeln(m1);

 A better way is using the function chunks;

     import std.range;

     auto m2 = a.chunks(3);
     writeln(m2);



Ok. Thank you for your help
Giovanni

Apr 04 2020

MoonlightSentinel <moonlightsentinel disroot.org> writes:

On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
wrote:
 Is there a Built-in function (no code, only a built-in function)
 that transform a linear array to a Matrix?

You can combine slide [1] and array [2]:

import std;

void main()
{
     auto input = [10,20,30,40,50,60,70,80,90,100,110,120];
     auto output = input.slide(3, 3).array;

     writeln(input);
     writeln();
     writeln(output);
}

Note that output is a view of input and not a copy.

[1] https://dlang.org/phobos/std_range.html#.slide
[2] https://dlang.org/phobos/std_array.html#.array

Apr 04 2020

Giovanni Di Maria <calimero22 yahoo.it> writes:

On Saturday, 4 April 2020 at 10:52:30 UTC, MoonlightSentinel 
wrote:
 On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
 wrote:
 Is there a Built-in function (no code, only a built-in 
 function)
 that transform a linear array to a Matrix?

 You can combine slide [1] and array [2]:

 import std;

 void main()
 {
     auto input = [10,20,30,40,50,60,70,80,90,100,110,120];
     auto output = input.slide(3, 3).array;

     writeln(input);
     writeln();
     writeln(output);
 }

 Note that output is a view of input and not a copy.

 [1] https://dlang.org/phobos/std_range.html#.slide
 [2] https://dlang.org/phobos/std_array.html#.array



Thank you very much.
Giovanni

Apr 04 2020

9il <ilyayaroshenko gmail.com> writes:

On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
wrote:
 Hi.
 Is there a Built-in function (no code, only a built-in function)
 that transform a linear array to a Matrix?

 For example:

 From

 [10,20,30,40,50,60,70,80,90,100,110,120];


 To

 [
 [10,20,30],
 [40,50,60],
 [70,80,90],
 [100,110,120]
 ];

 Thank You very much
 Cheers.
 Giovanni

You may want to look into a mir-algorithm package that supports 
rectangular multidimensional arrays like NumPy.

/+dub.sdl:
dependency "mir-algorithm" version="~>3.7.27"
+/

// http://mir-algorithm.libmir.org/mir_ndslice.html

import mir.ndslice;

void main()
{
     //
     auto intArray = [10,20,30,40,50,60,70,80,90,100,110,120];
     auto intMatrix = intArray.sliced(4, 3);

     static assert(is(typeof(intMatrix) == Slice!(int*, 2)));

     // lazy matrix
     auto lazyMatrix = iota!int([4, 3]/*shape*/, 10/*start*/, 
10/*stride*/);
     assert(intMatrix == lazyMatrix);
     //or
     foreach(i; 0 .. intMatrix.length)
     	foreach(j; 0 .. intMatrix.length!1)
         	assert(intMatrix[i, j] == lazyMatrix[i, j]);
         	
}

Apr 04 2020

Giovanni Di Maria <calimero22 yahoo.it> writes:

On Saturday, 4 April 2020 at 14:00:01 UTC, 9il wrote:
 On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
 wrote:
 [...]

 You may want to look into a mir-algorithm package that supports 
 rectangular multidimensional arrays like NumPy.

 [...]




Very good.
Thank you!!!!
G

Apr 04 2020

p.shkadzko <p.shkadzko gmail.com> writes:

On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
wrote:
 Hi.
 Is there a Built-in function (no code, only a built-in function)
 that transform a linear array to a Matrix?

 For example:

 From

 [10,20,30,40,50,60,70,80,90,100,110,120];


 To

 [
 [10,20,30],
 [40,50,60],
 [70,80,90],
 [100,110,120]
 ];

 Thank You very much
 Cheers.
 Giovanni

Why not use "chunks" from std.range?

import std.range: chunks;

void main() {
     int[] arr = [10,20,30,40,50,60,70,80,90,100,110,120];
     auto matrix1 = arr.chunks(3).chunks(4); // no allocation
     int[][][] matrix2 = arr.chunks(3).array.chunks(4).array;
}

But, keep in mind using array of arrays is not efficient.
For multidimensional arrays use Mir Slices.
If you need more information on how to create matrices, see this 
article: 
https://tastyminerals.github.io/tasty-blog/random/2020/03/22/multidimensional_arrays_in_d.html

Apr 05 2020

p.shkadzko <p.shkadzko gmail.com> writes:

On Sunday, 5 April 2020 at 18:58:17 UTC, p.shkadzko wrote:
 On Saturday, 4 April 2020 at 09:25:14 UTC, Giovanni Di Maria 
 wrote:
 [...]

 Why not use "chunks" from std.range?

 import std.range: chunks;

 void main() {
     int[] arr = [10,20,30,40,50,60,70,80,90,100,110,120];
     auto matrix1 = arr.chunks(3).chunks(4); // no allocation
     int[][][] matrix2 = arr.chunks(3).array.chunks(4).array;
 }

 But, keep in mind using array of arrays is not efficient.
 For multidimensional arrays use Mir Slices.
 If you need more information on how to create matrices, see 
 this article: 
 https://tastyminerals.github.io/tasty-blog/random/2020/03/22/multidimensional_arrays_in_d.html

it should be just one call to chunks --> arr.chunks(3), otherwise 
you'll get two nested arrays while you need only one. Sorry for 
confusion.

Apr 05 2020

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digitalmars.D.learn - Linear array to matrix