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Use Array.map on an 2-dimensional Array


Use Array.map on an 2-dimensional Array

By : Abraham
Date : October 17 2020, 06:10 PM
this one helps. So I have a 2-dimensional Array and want to use a "randomBool" function on each of the elements of the elements in the array. , You need to use two nested maps.
code :
const randomBools = test.map(outer => outer.map(inner => randomBool()))


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How does an N dimensional array with c-dimensional objects perform differently from an N dimensional array with C object

How does an N dimensional array with c-dimensional objects perform differently from an N dimensional array with C object


By : F.Society
Date : March 29 2020, 07:55 AM
I hope this helps you . The article seems to point out different ways to represent matrix data structures and the performance gains of a single array representation, although it doesn't really explain why you get the performance gains.
For example, to represent a NxNxN matrix:
code :
Cell {
   int x,y,z;
}
Matrix {
   int size = 10;
   Cell[] cells = new Cell[size];
}
Matrix {
    int size = 10;
    int[][][] data = new int[size][size][size];
}
Matrx {
    int size = 10;
    int[] data = new int[size*size*size];
}
How to create a function for flatten an array? Multi dimensional array to one dimensional array in Javascript

How to create a function for flatten an array? Multi dimensional array to one dimensional array in Javascript


By : thherman
Date : March 29 2020, 07:55 AM
may help you . I was reading ruby's array flatten function and looking for similar function in Javascript and didn't found. So, I created it myself. , So, here is the code I used to solve the solution.
code :
    var givenArr = [[1,2,[3]],4];
    var outputArray = [];

    function typeOf(value) {
      var s = typeof value;
      if (s === 'object') {
        if (value) 
          {
            if (Object.prototype.toString.call(value) == '[object Array]') {
              s = 'array';
            }
          }else{
          s = 'null';
        }
      }
      return s;
    }

    function getElementFromArray(array)
    {
        if(array.length == 0 ) return;
        for(var i = 0; i< array.length; i++ )
        {
            if( typeOf(array[i]) === 'array' )
            {
                getElementFromArray(array[i]);
            }else{
                 outputArray.push(array[i]);
            }
        }
     }//end getElementFromArray

     getElementFromArray(givenArr);

     console.log(outputArray);

     //output [1,2,3,4]
Extracting portions of low-dimensional numpy array into final axes of higher-dimensional array

Extracting portions of low-dimensional numpy array into final axes of higher-dimensional array


By : Katarzyna Leszczyńsk
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further One way would be with np.meshgrid to create 2D indexing meshes corresponding to the window of (n,n) shape, adding those with i0 that's extended with two new axes along which broadcasting would take place. Finally, we simply index into C to give us the desired 4D output. Thus, one implementation would be like so -
code :
N = np.arange(n)
X,Y = np.meshgrid(N,N)
out = C[i0[...,None,None] + Y,i0[...,None,None] + X]
In [153]: C
Out[153]: 
array([[3, 5, 1, 6, 3, 5, 8, 7, 0, 2],
       [8, 4, 6, 8, 7, 2, 6, 2, 5, 0],
       [3, 7, 7, 7, 3, 4, 4, 6, 7, 6],
       [7, 0, 8, 2, 1, 1, 0, 4, 4, 6],
       [2, 4, 6, 0, 0, 5, 6, 8, 0, 0],
       [4, 6, 1, 0, 5, 6, 2, 1, 7, 4],
       [0, 5, 5, 3, 7, 5, 7, 1, 4, 0],
       [6, 4, 4, 7, 2, 4, 6, 6, 6, 5],
       [5, 2, 3, 2, 2, 5, 4, 5, 2, 5],
       [3, 7, 1, 0, 4, 4, 6, 6, 2, 2]])

In [154]: i0
Out[154]: 
array([[1, 0, 4, 4],
       [0, 4, 4, 0],
       [2, 3, 1, 3],
       [2, 2, 0, 4]])

In [155]: n = 3

In [157]: out[0,0,:,:]
Out[157]: 
array([[4, 6, 8],
       [7, 7, 7],
       [0, 8, 2]])

In [158]: C[i0[0,0]:i0[0,0]+n,i0[0,0]:i0[0,0]+n]
Out[158]: 
array([[4, 6, 8],
       [7, 7, 7],
       [0, 8, 2]])
Can I copy string from two dimensional array to one dimensional array (Array&Pointers)

Can I copy string from two dimensional array to one dimensional array (Array&Pointers)


By : user2397597
Date : March 29 2020, 07:55 AM
should help you out I found quiet tricky in copying string from two dimensional array to one dimensional array. So I made access those value by address. It is working fine inside for loop. Is the one-dimensional array is really copied with two-dimensional array value. , You can use calloc for allocation temp pointer memory size.
code :
#include<stdio.h>
#include <stdlib.h>
#include<string.h>

int main()
{
    char *str[4] = {"i " "California", "ii " "Texas", "iii " "Florida", "iv " "Washington"};        //two dimensional array
    int r = 0;

    for(r = 0; r < 4; r++)
    {
        char *temp = (char*) calloc (strlen(str[r]) ,sizeof(char));
        strcpy(temp, str[r]);
        printf("%s", str[r]);
        printf("\n");
        free(temp);
    }
    return 0;
}
Convert multi-dimensional Numpy array to 2-dimensional array based on color values

Convert multi-dimensional Numpy array to 2-dimensional array based on color values


By : sutenm
Date : March 29 2020, 07:55 AM
To fix the issue you can do You could use giant lookup table. Let cls be [[0,0,0], [0,0,255], ...] of dtype=np.uint8.
code :
LUT = np.zeros(size=(256,256,256), dtype='u1')
LUT[cls[:,0],cls[:,1],cls[:,2]] = np.arange(cls.shape[1])+1
img_as_cls = LUT[img[...,0],img[...,1], img[...,2]]
def scalarize(x):
    # compute x[...,2]*65536+x[...,1]*256+x[...,0] in efficient way
    y = x[...,2].astype('u4')
    y <<= 8
    y +=x[...,1]
    y <<= 8
    y += x[...,0]
    return y
LUT = np.zeros(2**24, dtype='u1')
LUT[scalarize(cls)] = 1 + np.arange(cls.shape[0])
simg = scalarize(img)
img_to_cls = LUT[simg]
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