ChartView with a circular buffer?

[igor_stravinsky]

I've got a Quick Controls 2 chartView, in which I'd like to show the last 10 seconds of data from a running operation.

Adding on to my line series is fairly easy:

property int count:0

onMyValueChanged: {
                var parameterValue = value;
               myChartLineSeries.append(count,parameterValue);
                count++;
            }

But I can't figure out how to remove the oldest element in the line series when a new one is appended. Is there any easy way to do this without copying all the values in the LineSeries?

[oria66]

When you want to do this sort of bounded charts, you must pay attention to:

• How many points (x,y) you want to have in the Chart. I call it range.
• You must take care about the sample periodo to refresh your data. In this case, we call it x
• The axis and series data must be disengaged from the Chartview in ValueAxis and LineSeries components.

So, in a period you must realize each refresh.

// Here we bounded te data, removing the first element
if(lineseries.count > range){
       lineseries.remove(0)
}

// Append new values
lineseries.append(x, y)

//we establish the new min limit of x axis to the first value of the data
axisX.min = lineseries.at(0).x

// if the data have values, we establish the last value to max Limit in X axis
if(lineseries.count > 1){
     axisX.max = lineseries.at(lineseries.count - 1).x
}

This code works for me. Any question is welcome.

[drd1988on]

hi
I am also wants to use this kind of logic
When I give idaxisX.min = idLine.at(0),it is showing Error: Cannot assign QPointF to double

I wants to plot chart for every 1 second and the time should be the x axis label(the data is fetching from middleware )total 6 points have to show.
Regards
Divya

[6thC]

Just a guess but if you are indeed trying to assign a QPointF to and axis.min (or max) - in your example, try: = idLine.at(0).x() (or .y() )

If you want to manipulate the point x or y you'd modify a reference from the functions rx() and ry()

[oria66]

@drd1988on Ok, you are right, it seems I forgot the x in the line

axisX.min = lineseries.at(0).x

Does this solution work for you?

[drd1988on]

@oria66 yes.Thank you somuch.It worked .I have already corrected with adding.x to the line.
Now I wants to plot bar chart like the attchment
Ho wto show thw y value near each bars and how can i give this type of colour to the bars and reduce the width of each bar?

[oria66]

@drd1988on impressive chart! Congratulations!

I am thinking about your application, I think that level of detail you are not going to reach it only with qml. Maybe you must customize your own chart component using c++. Sincerely I do not know how to do it, but when you do it, can you post your solution? Kind regards.

[drd1988on]

@oria66 thank you