trend

Use to find out how a chart (array of values) are trending. Compares the last X points to the previous Y points before them.

Takes the maximum point of the last X points, and compares it to the average of the Y points before it.

Can ignore results if the average is below a certain minimum.

Returns null if the result is ignored (e.g., array is too small or average is too low).

Example

var trend = require('trend');
 
var chart = [10,11,9,31,12,14,15,24,26,18,0,0,0];
 
var growth = trend(chart, {
    lastPoints: 3,
    avgPoints: 10,
    avgMinimum: 10,
    reversed: false
});
 
if (growth < 0.25) console.log('The chart is going down! Is the server up?');
 

Usage

(array[, options])

Takes an array of numbers and calculates a trend.

Returns a number that says how much the chart is trending at the end, i.e. growth if >1 and decline if <1.

If the array is not long enough to calculate both an average over the last points and the rest it will return null.

Options

lastPoints

How many elements should be taken from the end of the array to calculate the last point.

The calculation is done by taking Math.max of the last lastPoints numbers.

Defaults to 1.

avgPoints

How many elements should be taken to calcuate an average.

Defaults to 10.

avgMinimum

Ignore (i.e. return null) if the average is below a minimum. This makes sure that we can ignore charts with low 'activity'.

No default value.

reversed

If your array is so that the newest entry is at the beginning, then use the reversed property.

Default is false.