Handling of array operations in C sharp

Question

I have been programming with Matlab for a couple of years. It handles operations on matrices and arrays quite easily.

Now, I am programming in C# and after reading for a while on sites such as http://msdn.microsoft.com/en-us/library/2s05feca.aspx and various other tutorial websites, I still have some questions.

In Matlab, something like this (written in a pseudo C# syntax) would work:

W[1][][] = new double[][]{{10,20,30},{40,50,60},};

where W is a 3 dimensional jagged array. The idea is that since the first dimension is defined (by 1 in this case), the assignation operation "understand" that the content of the 2 dimensional array provided is set to fill the two remainder dimensions of W. Then, how to get the same result or behaviour in C#?

Imagine the first dimension of W[][][] is a number associated with a city; the second, the age of every people living there and the third, their weight. Now lets have a portion of code that create a "calculation[][]" array containing ages and weights values. I want to assign the content of this array to W[1][][]. That is what I have failed to implement.

My objective is to do the equivalent of multiplication of matrices (and other relevant operations on matrices) using C#.

I read and read again a couple of explanations (can't list them all here) but it does not add up in my head, so I guess if someone could explain (again) how to manipulate multidimensional arrays in C#, it will help me understand how it works.

Thanks

On the left, W is a double[][][], while on the right you are creating a double[][] That doesn't match. If each dimension has the same length, a multidimensional array may be more convenient: double[,,] or double[,] — Dennis_E
– Dennis_E, Commented Jul 4, 2014 at 19:09
Sorry, my question is not clear. I know this syntax won't work directly in C#. Is there a way to assign two of the three dimensions of a jagged array at the same time. Imagine the first dimension of W[][][] is a number associated with a city; the second, the age of every people living there and the third, their weight. Now lets have a portion of code that create a "calculation[][]" array containing ages and weights values. I want to assign the content of this array to W[1][][]. That is what I have failed to implement — Doombot
– Doombot, Commented Jul 4, 2014 at 19:19

coolerfarmer · Accepted Answer · 2014-07-04 20:23:59Z

This isn't a 3 dimensional array. This is just an array of an array. I'm not really sure what you try to do.

Anyway, If I got u right u want to do something like this:

Nothing -.-

Ok, so if you need this for your example then I would recommend you a struct in order to do this easier. If you want to understand Multidimensional Arrays then you should reed the following:

You defined your 'Multidimensional Array' like this:

double[][][] array;

That's not a 'Multidimensional Array'. This is an array (list) of an array of an array.

A real 'Multidimensional Array' is defined this (3 dimensions):

double[,,] array;

That's a difference :D

if u use the 'real Multidimensional Array' then u can do the above like this;

private static void Main(string[] args)
{
    var raw = new double[,,]
    {
        {
            {1, 2},
            {3, 4}
        },
        {
            {5, 6},
            {7, 8}
        }
    };

    Console.WriteLine(raw[0, 0, 0]); //1
    Console.WriteLine(raw[1, 1, 0]); //7
    Console.ReadKey();
}

And this would be the code for the array of an array of an array

var raw = new double[][][]
{
    new double[][]
    {
        new double[]
        {
            1,
            3
        },
        new double[]
        {
            2,
            4
        }
    },
    new double[][]
    {
        new double[]
        {
            5,
            7
        },
        new double[]
        {
            6,
            8
        }
    }
};
Console.WriteLine(raw[0][0][0]); //1
Console.WriteLine(raw[1][1][0]); //6
Console.ReadKey();

In your case (if you don't want to use a struct) than this array would be the better way!

A struct for your case would look like this:

    private static void Main(string[] args)
    {
        var raw = new SampleDataStruct[2]
        {
            new SampleDataStruct
            {
                CityName = "New York", AgeWeight = new AgeWeightStruct[3]
                {
                    new AgeWeightStruct{Age = 50,Weigth = 70},
                    new AgeWeightStruct{Age = 40,Weigth = 75},
                    new AgeWeightStruct{Age = 30,Weigth = 65}
                }
            },

            new SampleDataStruct
            {
                CityName = "Berlin", AgeWeight = new AgeWeightStruct[3]
                {
                    new AgeWeightStruct{Age = 50,Weigth = 65},
                    new AgeWeightStruct{Age = 40,Weigth = 60},
                    new AgeWeightStruct{Age = 30,Weigth = 55}
                }
            }
        };

        Console.WriteLine(raw.Where(st => st.CityName == "Berlin").ElementAtOrDefault(0).AgeWeight.Where(aw => aw.Age == 40).ElementAtOrDefault(0).Weigth); //Berlin -> Age = 40 -> Display Weight (60)
        Console.WriteLine(raw.Where(st => st.CityName == "New York").ElementAtOrDefault(0).AgeWeight.Where(aw => aw.Age == 30).ElementAtOrDefault(0).Weigth); //New York -> Age = 30 -> Display Weight (65)
        Console.ReadKey();
    }
}

public struct SampleDataStruct
{
    public string CityName;
    public AgeWeightStruct[] AgeWeight;
}

public struct AgeWeightStruct
{
    public int Age;
    public int Weigth;
}

Ah a struct is what I was looking for. Dumb me I use them in Matlab forgot they were in Csharp too...

Eugene Podskal · Accepted Answer · 2014-07-04 19:29:48Z

1

You can do it so:

            Int32 firstDimensionSize = 3;
            double[][][] matrix3D = new double[firstDimensionSize ][][];

            matrix3D[1]= new double[][]
            { 
                new double[]{10,20,30}, 
                new double[]{40,50,60},
            };

Because matrix3D is an array of arrays of arrays. Each its element is double[][] - 2D jagged array. Just don't forget that matrix3D[0] and matrix3D[2] will be uninitialized - null.

answered Jul 4, 2014 at 19:29

Eugene Podskal

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2 Comments

Doombot Over a year ago

Makes me think, just another question: Is there some way to incorporate a for loop to initialize all values to 0? Instead of having new double[]{0,0,0,0,0,0 ... 0} one thousand time?

Doombot Over a year ago

Ok it seems I can do this: double[] banana = new double[]{}; for(int i=0,i<1000,i++) { banana[i]=0; } then: matrix3D[1]= new double[][] { banana, banana, };

Dennis_E · Accepted Answer · 2014-07-04 19:31:46Z

1

var W = new double[][][]
{
    new double[][]{
        new double[] {1,2,3}, new double[] {4,5,6}
    },
    new double[][]{
        new double[] {7,8,9}, new double[] {10,11,12}
    }
};

Alternatively, you can use a double[,,] if the dimensions are the same:

var W = new double[,,]
{
    {
        {1,2,3}, {4,5,6}
    },
    {
        {7,8,9}, {10,11,12}
    }
};

answered Jul 4, 2014 at 19:31

Dennis_E

8,90426 silver badges32 bronze badges

1 Comment

Doombot Over a year ago

Sorry I am not yet allowed to upvote but it works too! Thanks!

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