javascript - 将线性阵列转换为矩阵的有效方法

Question

我有一个数组，其中包含一个带有 x 坐标、y 坐标和矩阵值的子数组:

// [x,y,value]
var arr = [
[1,2,0.01],
[1,3,0.02],
[1,4,0.05],
[1,5,0.03],
[2,3,0.04],
[2,4,0.02],
[2,5,0.01],
[3,4,0.06],
[3,5,0.05],
[4,5,0.07],
]

然后我有一个 x_max X x_max 维度的零填充二维数组(“矩阵”)。我正在尝试使用一种计算有效的方法来填充该矩阵的值，如下所示:

// already have a variable called 'matrix' which is zero-filled

function constructMatrix(){
    for(var i in arr){
        var y = arr[i][0];
        var x = arr[i][1];
        var val = arr[i][2];
        matrix[y][x] = val;
    }
}

我得到的是一个具有唯一列值但行间值相同的矩阵。我的逻辑是否有一个简单的突破？

我期望输出如下:

var matrix = [
[0.01,0.02,0.05,0.03],
[0,0.04,0.02,0.01],
[0,0,0.06,0.05],
[0,0,0,0.07],
]

Answer 1

你可以这样做:

var arr = [
    [1, 2, 0.01], [1, 3, 0.02], [1, 4, 0.05], [1, 5, 0.03],
    [2, 3, 0.04], [2, 4, 0.02], [2, 5, 0.01], [3, 4, 0.06],
    [3, 5, 0.05], [4, 5, 0.07]
];

// find total number of rows and columns
// add 1 because (x = 5) == (index 6)    // indexes start at 0
var rows = arr.reduce((x,y) => Math.max(x, y[0]), 0) + 1;
var columns = arr.reduce((x,y) => Math.max(x, y[1]), 0) + 1;

// initiate an empty matrix 
var matrix = [...Array(rows)].map(() => Array(columns).fill(0));

// loop over the points
arr.forEach(function(point) {
    var x = point[0];
    var y = point[1];
    var val = point[2];
    matrix[x][y] = val;
});

// your result
console.log(  JSON.stringify(matrix, 0, 2)  );

.as-console-wrapper {
  max-height: 100%!important;
}