Correlation formula explanation needed d3.js
- by divakar
function getCorrelation(xArray, yArray) {
alert(xArray);
alert(yArray);
function sum(m, v) {return m + v;}
function sumSquares(m, v) {return m + v * v;}
function filterNaN(m, v, i) {isNaN(v) ? null : m.push(i); return m;}
// clean the data (because we know that some values are missing)
var xNaN = _.reduce(xArray, filterNaN , []);
var yNaN = _.reduce(yArray, filterNaN , []);
var include = _.intersection(xNaN, yNaN);
var fX = _.map(include, function(d) {return xArray[d];});
var fY = _.map(include, function(d) {return yArray[d];});
var sumX = _.reduce(fX, sum, 0);
var sumY = _.reduce(fY, sum, 0);
var sumX2 = _.reduce(fX, sumSquares, 0);
var sumY2 = _.reduce(fY, sumSquares, 0);
var sumXY = _.reduce(fX, function(m, v, i) {return m + v * fY[i];}, 0);
var n = fX.length;
var ntor = ( ( sumXY ) - ( sumX * sumY / n) );
var dtorX = sumX2 - ( sumX * sumX / n);
var dtorY = sumY2 - ( sumY * sumY / n);
var r = ntor / (Math.sqrt( dtorX * dtorY )); // Pearson ( http://www.stat.wmich.edu/s216/book/node122.html )
var m = ntor / dtorX; // y = mx + b
var b = ( sumY - m * sumX ) / n;
// console.log(r, m, b);
return {r: r, m: m, b: b};
}
I have finding correlation between the points i plot using this function which is not written by me. my
xarray=[120,110,130,132,120,118,134,105,120,0,0,0,0,137,125,120,127,120,160,120,148]
yarray=[80,70,70,80,70,62,69,70,70,62,90,42,80,72,0,0,0,0,78,82,68,60,58,82,60,76,86,82,70]
I can t able to understand the function perfectly. Can anybody explain it with the data i pasted here. I also wanted to remove the zeros getting calculated from this function.
