How to know all rows of which column in matrix has data?

diamond diamond

Hi
I have a matrix, I want to know which rows of first column has data , and if first row has data I check the other columns to have a data.

m= 1 0 0 1
0 1 1 0
1 1 1 0
in this matrix, the first column has 2 data, first and third rows. At this time I see the other column in frist row and I get that third column has data, I compute Jaccard similarity for first and third rows

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes13y ago
Accepted answer
OK, try this then:

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
static void Main()
{
int[,] m = new int[3, 4]{{1, 0, 0, 1}, {0, 1, 1, 0}, {1, 1, 1, 0}};
var rows = new List();

// find which rows have a first column containing a non-zero value
for(int i = 0; i < m.GetLength(0); i++)
{
if(m[i,0] != 0) rows.Add(i);
}

if (rows.Count == 2)
{
Console.WriteLine("The following rows have data in the first column\n");
PrintRow(m, rows[0]);
PrintRow(m, rows[1]);
Console.WriteLine("The Jaccard similarity coeffcient is {0}",Jaccard(m, rows[0], rows[1]));
}

Console.ReadKey();
}

static double Jaccard(int[,] m, int r1, int r2)
{
int[] a = new int[m.GetLength(1)];
int[] b = new int[m.GetLength(1)];
for(int j = 0; j < m.GetLength(1); j++)
{
a[j] = m[r1, j];
b[j] = m[r2, j];
}

return (double)a.Intersect(b).Count()/a.Union(b).Count();
}

static void PrintRow(int[,] m, int r)
{
Console.Write("(");

for(int j = 0; j < m.GetLength(1); j++)
{
Console.Write(m[r,j]);
if (j < m.GetLength(1) - 1) Console.Write(",");
}
Console.WriteLine(")");
}

}
diamond diamond13y ago
I appreciated you for your response.
But my matrix is created as below, I save src IP addresses in every time window, rows are src Ip address and columns are time window.
int[,] Failure_matrix = new int[5, size];

I want to know which src ip addresses are seen in current time window(be 1 in matrix), it is saved in first column of matrix. my Jaccard similarity is different from what is you have written, I want acquire intersect of src ip address are 1 in current time window with other time windows (columns). I mean, if I see one src ip is 1 in current time window, I see the others time windows that this src ip was 1 and other src ipadddres that time window are 1, then I compute their union and intersect by Jaccard
Vulpes13y ago
I only followed some of that but the following may help you to figure out what you need.

I've only dealt with the case where 2 rows contains data in the first column as I wasn't sure what to do in other scenarios.

Note that it's convenient here to express the matrix as a jagged array even though the lengths of all the rows are, of course, the same. This is because one can easily extract a whole row from the jagged array:

using System;
using System.Linq;

class Program
{
static void Main()
{
int[][] m = new int[3][];
m[0] = new int[]{1, 0, 0, 1};
m[1] = new int[]{0, 1, 1, 0};
m[2] = new int[]{1, 1, 1, 0};

// find which rows have a first column containing 1
int[][] rows = m.Where(e => e[0] == 1).ToArray();

if (rows.Length == 2)
{
Console.WriteLine("The following rows have data in the first column\n");
PrintRow(rows[0]);
PrintRow(rows[1]);
Console.WriteLine("The Jaccard similarity coeffcient is {0}",Jaccard(rows[0], rows[1]));
}

Console.ReadKey();
}

static double Jaccard(int[] a, int[] b)
{
int m11 = 0;
int m01 = 0;
int m10 = 0;

for (int i = 0; i < a.Length; i++)
{
if (a[i] == 1 && b[i] == 1)
m11++;
else if (a[i] == 0 && b[i] == 1)
m01++;
else if(a[i] == 1 && b[i] == 0)
m10++;
}

return (double)m11/(m01 + m10 + m11);
}

static void PrintRow(int[] a)
{
Console.Write("(");

for(int i = 0; i < a.Length; i++)
{
Console.Write(a[i]);
if (i < a.Length - 1) Console.Write(",");
}
Console.WriteLine(")");
}

}