Converting between chart space and local space

When building custom interactions with the data series chart, it is important to be able to transition between unity’s local space and the chart space. In this way , you can convert a point on the chart to a point on the canvas and vise versa.

What are the chart space and local space

• Local Space – are coordinates in the data series chart’s RectTransform component. the coordinates can be converted to canvas space by calling transform.transformPoint(localSpace)
• Chart Space – are coordinates within the chart axis system.

Conversion methods

// converts a chart space coordinate into local space coordinate
public Vector3 ChartSpaceToLocalSpace(DoubleVector3 chartSpace)

//converts local space coordinate into chart space coordinate
public DoubleVector3 LocalSpaceToChartSpace(Vector3 localSpace)

You can call these methods in the following way

// covert the vector (1,1) in chart units to local space
Vector3 localSpace = chart.Axis.ChartSpaceToLocalSpace(new DoubleVector3(1,1,0));

// convert the vector in local space back to chart space
DoubleVector3 chartSpace = chart.Axis.LocalSpaceToChartSpace(localSpace);

Checking if the coordinates are within bounds

Once you have converted the coordinates , you may want to check if they are within the bounds of the visible local/chart space. Have a look at the following calls:

Vector3 localSpace = chart.Axis.ChartSpaceToLocalSpace(new DoubleVector3(1,1,0));

// returns true if local point is inside the data series chart's RectTransform
Chart.Axis.LocalViewContains(localPoint); 

USe case example

In the indicator interaction (CanvasIndicatorInteraction.cs) places an interactive indicator on top of the chart. Here are some points of interest in this interaction

// this method finds the point at index i and returns it's local space position        
public Vector3 GetPointLocalSpace(string category,int index,out DoubleVector3 chartSpace)
        {
            chartSpace = Chart.DataSource.GetCategory(category).Data.GetPointAt(index);
            return Chart.Axis.ChartSpaceToLocalSpace(chartSpace);
        }
.
.
.
// the indicator is placed at the local space point
           Vector3 localPoint = GetPointLocalSpace(category, index,out chartPoint);
            Indicator.anchoredPosition = localPoint;
.
.
.
// if the point is outside the bounds of the chart, the indicator is disabled
            if (Chart.Axis.LocalViewContains(localPoint))
                Indicator.gameObject.SetActive(true);
            else
                Indicator.gameObject.SetActive(false);