get tickpositions highcharts - highcharts

Question

I have a highcharts scatter plot for which I'm trying to fetch the x and y tickPositions in freemarker template, specifically the first and last one. Such as that I would get something as [-10,-10] (bottom left corner) at the intersection of the x-y axis and [30,40] (top right corner) at the intersection of the opposite sides, where xAxis ticks are [-10,0,10,20,30] and yAxis ticks are [-10,0,10,20,30,40]
I want these points so that I'll be able to plot a diagonal line across the scatter plot from bottom lower corner to top right corner. The line series should look like:
series: [
{
type : 'line',
<#--diagonal line-->
data :[[-10,-10], [30,40]], // to be calculated dynamically
lineWidth: 0.5,
marker : {
enabled : false
}
},
{
color: 'rgb(0,85,152)',
data: [[2,3],[6,7],[8,9]]
}
]
The problem at present is I'm unable to get [-10,-10], [30,40] data points. Is it even possible is what I'm wondering. Any help is much appreciated!

Answer 1

You have the getExtremes() function on an axis.
For example:
var extremes = $('#container').highcharts().yAxis[0].getExtremes();
Here is the doc, and here is a demo fiddle
Is this what you were trying to achieve ?
Edit
After your fiddle example, I understand better your need.
Here is the updated fiddle
var chart = $('#container').highcharts();
var extremeY = chart.yAxis[0].getExtremes();
var extremeX = chart.xAxis[0].getExtremes();
var lineSeries = {
type: 'line',
data: [
[extremeX.min, extremeY.min],
[extremeX.max, extremeY.max]
],
lineWidth: 0.5,
lineColor: 'rgb(0,0,0)',
marker: {
enabled: false
}
};
chart.addSeries(lineSeries);
I created an object with the properties of the line series. And using min and max (not dataMin and dataMax) properties from the object returned by getExtremes() you obtain the desired result.
Edit 2
You could put this code in the load event of the chart. It is a callback called after the chart finished loading. And here you can use this to refer to the chart :
$('#container').highcharts({
chart: {
events: {
load: function() {
var extremeY = this.yAxis[0].getExtremes();
var extremeX = this.xAxis[0].getExtremes();
var lineSeries = {
type: 'line',
data: [
[extremeX.min, extremeY.min],
[extremeX.max, extremeY.max]
],
lineWidth: 0.5,
lineColor: 'rgb(0,0,0)',
marker: {
enabled: false
}
};
this.addSeries(lineSeries);
}
},
//...
});
Here is the new updated fiddle

Answer 2

Since you need only a diagonal path, then you could add it using renderer
Example: http://jsfiddle.net/cr7gq4st/
function diagonal() {
var chart = this,
ren = chart.renderer,
diag = chart.diag,
attrs = {
'stroke-width': 0.5,
stroke: '#000',
zIndex: 1
},
topR = {
x: chart.plotLeft + chart.plotWidth,
y: chart.plotTop
},
bottomL = {
x: chart.plotLeft,
y: chart.plotTop + chart.plotHeight
},
d = 'M ' + bottomL.x + ' ' + bottomL.y + ' L ' + topR.x + ' ' + topR.y;
if( !diag ) { //if doesn't exist, then create
chart.diag = ren.path().attr(attrs).add();
}
chart.diag.attr({d:d});
}