mansj
Posts: 5
Joined: Thu Feb 04, 2010 8:41 am

spline and false negatives

Hello,

I am currently trying to load dynamic data from a text file into a line chart, and getting some strange errors. See the attached image. In six places the line goes below zero, and the yAxis is also displaying values below zero. However, the data loaded has NO negative values, and this is correctly indicated upon hovering the line.

So, why is the line going below zero?
Attachments
Skärmavbild 2010-02-08 kl. 14.11.29.png
Skärmavbild 2010-02-08 kl. 14.11.29.png (28.53 KiB) Viewed 3557 times
mansj
Posts: 5
Joined: Thu Feb 04, 2010 8:41 am

Re: spline and false negatives

Here is the complete calling code for that chart:

Code: Select all

var chart3 = new Highcharts.Chart({
         chart: {
            renderTo: 'chart2',
            defaultSeriesType: 'spline'
         },
         title: {
            text: 'Domäntillväxt'
         },
        plotOptions: {
			spline: {
				lineWidth: 1,
				marker: {
					enabled: false
		         	},
		     	states: {
	            	hover: {
						marker: {
							enabled: true,
								symbol: 'circle',
								radius: 2
							}
	            		}
	         		}
	      		}
    	     },
		tooltip: {
			formatter: function() {
            	return '<b>'+ this.series.name +'</b><br/>'+
            	Highcharts.dateFormat('%e %b %Y', this.x) +': '+ this.y;
      			}
			},
         xAxis: {
         	labels: {
         		enabled: true
         	},
         	type: 'datetime'
         },
         yAxis: {
            title: {
               text: 'Dom&auml;ner',
               enabled: false
            }
         },
         legend: {
         	enabled: false
        	},
         series: [{
            name: 'Dom&auml;ner',
            data: [[Date.UTC(2009, 10, 06), 22],[Date.UTC(2009, 10, 07), 23],[Date.UTC(2009, 10, 08), 48],[Date.UTC(2009, 10, 09), 44],[Date.UTC(2009, 10, 10), 6630],[Date.UTC(2009, 10, 11), 3],[Date.UTC(2009, 10, 12), 33],[Date.UTC(2009, 10, 13), 28],[Date.UTC(2009, 10, 14), 135],[Date.UTC(2009, 10, 15), 64],[Date.UTC(2009, 10, 16), 57],[Date.UTC(2009, 10, 17), 68],[Date.UTC(2009, 10, 18), 20],[Date.UTC(2009, 10, 19), 9],[Date.UTC(2009, 10, 20), 33],[Date.UTC(2009, 10, 21), 28],[Date.UTC(2009, 10, 22), 74],[Date.UTC(2009, 10, 23), 110],[Date.UTC(2009, 10, 24), 69],[Date.UTC(2009, 10, 25), 23],[Date.UTC(2009, 10, 26), 105],[Date.UTC(2009, 10, 27), 73],[Date.UTC(2009, 10, 28), 61],[Date.UTC(2009, 10, 29), 44],[Date.UTC(2009, 10, 30), 55],[Date.UTC(2009, 11, 01), 13],[Date.UTC(2009, 11, 02), 9],[Date.UTC(2009, 11, 03), 20],[Date.UTC(2009, 11, 04), 20],[Date.UTC(2009, 11, 05), 36],[Date.UTC(2009, 11, 06), 35],[Date.UTC(2009, 11, 07), 43],[Date.UTC(2009, 11, 08), 15],[Date.UTC(2009, 11, 09), 2],[Date.UTC(2009, 11, 10), 7901],[Date.UTC(2009, 11, 11), 19],[Date.UTC(2009, 11, 12), 57],[Date.UTC(2009, 11, 13), 46],[Date.UTC(2009, 11, 14), 59],[Date.UTC(2009, 11, 15), 66],[Date.UTC(2009, 11, 16), 7],[Date.UTC(2009, 11, 17), 23],[Date.UTC(2009, 11, 18), 24],[Date.UTC(2009, 11, 19), 18],[Date.UTC(2009, 11, 20), 37],[Date.UTC(2009, 11, 21), 41],[Date.UTC(2009, 11, 22), 66],[Date.UTC(2009, 11, 23), 28],[Date.UTC(2009, 11, 24), 128],[Date.UTC(2009, 11, 25), 81],[Date.UTC(2009, 11, 26), 57],[Date.UTC(2009, 11, 27), 63],[Date.UTC(2009, 11, 28), 55],[Date.UTC(2009, 11, 29), 21],[Date.UTC(2009, 11, 30), 5],[Date.UTC(2009, 11, 31), 25],[Date.UTC(2010, 0, 01), 29],[Date.UTC(2010, 0, 02), 23],[Date.UTC(2010, 0, 03), 35],[Date.UTC(2010, 0, 04), 30],[Date.UTC(2010, 0, 05), 31],[Date.UTC(2010, 0, 06), 6],[Date.UTC(2010, 0, 07), 24],[Date.UTC(2010, 0, 08), 54],[Date.UTC(2010, 0, 09), 12],[Date.UTC(2010, 0, 10), 8886],[Date.UTC(2010, 0, 11), 21],[Date.UTC(2010, 0, 12), 62],[Date.UTC(2010, 0, 13), 13],[Date.UTC(2010, 0, 14), 18],[Date.UTC(2010, 0, 15), 50],[Date.UTC(2010, 0, 16), 52],[Date.UTC(2010, 0, 17), 41],[Date.UTC(2010, 0, 18), 27],[Date.UTC(2010, 0, 19), 24],[Date.UTC(2010, 0, 20), 22],[Date.UTC(2010, 0, 21), 16],[Date.UTC(2010, 0, 22), 60],[Date.UTC(2010, 0, 23), 90],[Date.UTC(2010, 0, 24), 126],[Date.UTC(2010, 0, 25), 90],[Date.UTC(2010, 0, 26), 57],[Date.UTC(2010, 0, 27), 34],[Date.UTC(2010, 0, 28), 52],[Date.UTC(2010, 0, 29), 122],[Date.UTC(2010, 0, 30), 40],[Date.UTC(2010, 0, 31), 21],[Date.UTC(2010, 1, 01), 58],[Date.UTC(2010, 1, 02), 19],[Date.UTC(2010, 1, 03), 12]]
         }]
      });
      
      
      
   });
torstein.honsi
Site Admin
Posts: 9215
Joined: Thu Nov 09, 2006 11:22 am
Location: Vik i Sogn, Norway

Re: spline and false negatives

Hi Mansj,

This is how splines are supposed to behave. Take a look at http://www.math.ucla.edu/~baker/java/hoefer/Spline.htm. If you drag one of the middle points up or down, you'll see a negative bulge appearing on both sides of the closest points. For series like yours with a high fluctuation, line series is probably a better option.
Torstein Hønsi
CTO, Founder
Highsoft
mansj
Posts: 5
Joined: Thu Feb 04, 2010 8:41 am

Re: spline and false negatives

Wow. The more you know, huh? Thanks!

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