Dynamically create index in two dimensional array

Question

Having some trouble with this script. It iterates through a two dimensional array and adds each corresponding index together. So basically arr[0][1] + arr[0][2] + arr[0][3] ... arr[1][1] + arr[1][2] + arr[1][3] ...etc.

This first one works fine. So my logic is ok. My problem here is that I can't create the indices dynamically. I don't think a push will work since I'm summing values here.

var cat_stats_week_radar = [[0,0,0,0,0,0,0,0,0,0,0,0,0,0]];


    for (var i = 0; i < cat_stats_week.length; i++) {
        for (var j = 0; j < cat_stats_week[0].length; j++) {
            cat_stats_week_radar[0][j] += +(cat_stats_week[i][j]);
        }

}

This one doesn't work, I don't get an error, just a bunch of NaN values.

var cat_stats_week_radar = [[]];


    for (var i = 0; i < cat_stats_week.length; i++) {
        for (var j = 0; j < cat_stats_week[0].length; j++) {
            cat_stats_week_radar[0][j] += +(cat_stats_week[i][j]);
        }

}

Here are the arrays I'm working with.

Array to add:

var cat_stats_week = [
[0,0,0,0,0,0,0,1,0,0,0,0,0,0],
[0,0,0,0,0,0,1,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[0,0,0,0,0,0,1,0,0,0,0,0,0,0],
[0,0,0,0,0,0,0,0,0,0,0,0,1,0],
[0,0,0,0,0,0,0,0,0,0,0,0,1,0],
[0,0,1,0,0,0,0,0,0,0,0,0,0,0]
];

Resulting array:

var cat_stats_week_radar = [[0, 0, 1, 0, 0, 0, 2, 1, 0, 0, 0, 0, 2, 0]];

Blender · Accepted Answer · 2013-04-15 21:18:18Z

2

You need to initialize it with the right number of zeroes:

var cat_stats_week_radar = [[]];

for (var i = 0; i < cat_stats_week[0].length; i++) {
    cat_stats_week_radar[0].push(0);
}

And with Underscore.js:

_.map(_.zip.apply(null, cat_stats_week), function(a) {
    return _.reduce(a, function(a, b) {
        return a + b
    })
});

answered Apr 15, 2013 at 21:18

Blender

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