Javascript unidimensional to multidimensional array

Question

I have a unidimensional array filled up with graphic point coordinates that i get from a JSON encoded string, on which i

jsdata = $.parseJSON('[' + strdata + ']');

arr = jsdata[0].toString().split(',');

and i don't seem to quite think up the algorigthm to parse it to a 3 dimensional array, which needs to have the following structure:

 data['parameter to plot'][point][coordinate]

As an example, let's say i'm gonna draw a line graph with data from 2 parameters. It will draw 74 points with 2 coordinates for each of the 2 lines which means the array's index will go as far as:

arr[296];

So, the "data" array's indexes will need to go as far as:

 data[1][74][1];

I have no problem creating any of the arrays, but developing an algorithm for filling up the "data" array according to "arr's" length is really baking my brain. :/

Thanks for any help bros.

EDIT:

Since i don't know how many parameters i'm gonna need to draw graphs for but i'll know which type of graph i'm going to use, i came up with this answer.

I create a multi dimensional array using this function

function createArray(length) {
  var arr = new Array(length || 0),
      i = length;

  if (arguments.length > 1) {
    var args = Array.prototype.slice.call(arguments, 1);
    while(i--) arr[i] = createArray.apply(this, args);
  }        
  return arr;
 }

And then i can do

function toMulti(arr, plotType)
 {

    if(plotType =='line_plot')
    {
        var lineaux = createArray((arr.length/74/2),arr.length/2,2);
        var cont = 0;
        for(i= 0; i<lineaux.length; i++)
            for(j=0; j< lineaux[i].length; j++)
                for(k=0; k< lineaux[i][j].length;k++)
                {
                    lineaux[i][j][k] = arr[cont];
                    cont +=1;
                }
        return lineaux;
    }
}

But a line graph will not always have 74 points, nor will i always plot line graph..

Tell me what you think about it and if you can think up any way to make this non-plotType dependent i'd be eternally grateful. Or just buy you a beer to make it even. :D

It isn't. it's something like arr[0] = 'x coordinate', arr[1]= 'y coordinate' and so on. — nanominimicro
– nanominimicro, Commented Sep 13, 2013 at 11:18
How "so on"? arr[2] = 'z coordinate', or arr[2] = 'second x coordinate', or what is it? Show us a sample, maybe by JSON.stringify(arr, null, 4) — Bergi
– Bergi, Commented Sep 13, 2013 at 11:25
Sorry i led you to ambiguous interpretation. :/ yes, arr[2]='2nd x coordinate', arr[3]='2nd y coordinate', arr[4]='3rd x coordinate'. arr is already parsed from a JSON string, by using jQuery.parseJSON and spliting commas. could i parse it any other way that would make this simpler? — nanominimicro
– nanominimicro, Commented Sep 13, 2013 at 13:37

GameAlchemist · Accepted Answer · 2013-09-16 10:04:21Z

2

You need to have two vars, parameterCount, and pointCount.
Then the size of your data array is 2*parameterCount*PointCount (in 2d).

function toMulti(data, parameterCount) { 
   var pointCount = data.length / ( 2 * parameterCount );
   var res = [];
   for (var pr=0 ; pr<parameterCount ; pr ++) {
        var newLine = [];
         for (var pt=0; pt<pointCount; pt++ ) {
              var newPoint  = [data[2*pr*pointCount+2*pt],data[2*pr*pointCount+2*pt+1]]
              newLine.push(newPoint);
         }
        res.push(newLine);
   }
   return res;
}

Just to explain a little :
parameterCount is the... parameter count, and is the first dimension of the multi-dimensionnal array.
pointCount is the second dimension
the third dimension is 2D, the x and the y of the point.

The points are supposed to be organized like this within the array :
[ param1x1, param1y1, param1x2, param1y2, param1x3, param1y3, ... param1xpointCount, param1ypointCount, param2x1, param2y1, param2x2, param2y2, param2x3, .... , param2xpointCount, param2ypointCount, ..., paramparameterCountx1, paramparameterCounty1, ... paramparameterCountxpointCount, paramparameterCountypointCount]

(sorry i can't use here the math notation that would make all this look less messy.)

Edit : provided it is a 2D set of points, and you know the parameter count, you have

 var pointCount = data.length / ( 2 * parameterCount );

i updated the code.

edited Sep 16, 2013 at 10:04

answered Sep 13, 2013 at 11:27

GameAlchemist

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4 Comments

nanominimicro Over a year ago

I won't know how many parameters i'm gonna plot data for. I need to get that from arr[]'s index.

nanominimicro Over a year ago

newPoint ou thisPoint?

nanominimicro Over a year ago

Well, i may have a way to know how many parameters i'll have, but no PointCount, for sure... :/

nanominimicro Over a year ago

though your answer is correct, my question is now irrelevant. I went around all this parsing logic and managed to use jQuery's $.getJSON(), which returns me what i want. Nonetheless, i'll mark your answer as the answer.

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