Customised size of x data points and Scatter Graph with Linear Trend Line

[NyoSeintLay]

Hi Daniel,

Thanks for your awesome library and I have full of hopes that your library can be useful in my first swift application.
I just started a few graphs and stucking on one part.
I would like to create in final is scatter graph with Linear trendline as shown in figure A.
Now I am getting with this lib is as shown in Figure B.

Question 1
Could we change customised size of X-data points ?
now X-axis data point are always same size.
For eg -
Xaxis - 4.7, 9.41, 18.81, 37.6, 75.6
Yaxis - 0.035, 0.146, 0.373, 0.912, 2.276
Question 2
How can I draw Linear trend line (if possible - R square value included)?

I was wondering if you or other contributors can reply my questions.

Thanks and Regards,
NyoSeint Lay

[liuxuan30]

Q1: X axis is index based axis currently, so you can't; however, the good news is both Android and iOS library is working on v3.0 to support this. It should be coming soon, but no ETA yet; remember to watch this repo:)

You can of course tweak this library to draw figure a, but I don't think it's a smart choice for you, so just wait.

Q2: drawing trend lines requires knowledge of CoreGraphics; if you are not familiar with it, grab some tutorials; basically, you should know the (x,y) pairs to connect as trend lines if it's not linear.

for linear trend line, consider y = kx+b, so you only need two pairs to draw the line
for figure b, if you are familiar with cubic line drawing, then you can just connect those 5 points; if not, then you probably need like 100 data points to connect as line segment as a curve;(more points means smoother, right?)

You can take your figure b data to draw it as cubic line first to see if it meets your goals; to draw as cubic, set LineChartDataSet.mode = HorizontalBezier or CubicBezier

To get started, take a look at how ChartLimitLine is implemented; for cubic line, check drawHorizontalCubic() implementations

[liuxuan30]

I just saw v3.0 branch synced with master. You can be the first user.. :) use at your own risk

[NyoSeintLay]

Ohh .. yes. How good luck I am.
Just now I was tested with V3 by using new " iChartDataSet"
ChartDataEntry parameter Changes
ChartDataEntry(value: values[i], xIndex: i) -> ChartDataEntry(x: xPoints[i],y: yPoints[i])

Now I am facing one issue is to add ChatDataEntry objects to iChartDataSet array.
I cannot create iChartDataSet object (may be don't know how to do)
Could u give me some advice for this ?
Thanks in advance, I will be grateful for any help you can provide.

The following is my setChart Function code:

var iChartDataSets: [IChartDataSet] = []
for i in 0..<xPoints.count {
// let dataEntry = ChartDataEntry(value: values[i], xIndex: i)

        let dataEntry = ChartDataEntry(x: xPoints[i],y: yPoints[i])

        let iChartDataset = ?? //Need to create IChartDataSet Object
        iChartDataSet.addEntry(dataEntry)

        iChartDataSets.append(iChartDataset)

    }

    let scatterChartData = ScatterChartData(dataSets: iChartDataSets)
    scatterChartView.data = scatterChartData
    scatterChartView.xAxis.labelPosition = .Bottom

[liuxuan30]

you should not use iChartDataSet, they are protocols. Use Concrete classes from standard implementation

[NyoSeintLay]

Thats right.. my mistake.. I was on leave and cannot get back to this issue
Thanks for your advice.
Now I can set value (x,y) with customised x axis with V3 Library.
^.^