QCustomPlot in real time in an ECG style

Question

I want to make a real time graph to plot the data from my Arduino and I want to use the following function from QCustomPlot to plot the graph in an ECG style (starting again after few seconds and replacing the previous data):

void QCPGraph::addData(const QVector<double> &keys, const QVector<double> &values)`

with keys=time and values=data from serial port.

I already have the serial data and a graph that is continuous but I don't know how to modify this with the function above and make time vector.

Can you give me an example of how to call that function?

Answer 1

If I get it right, you have a graph that it's xAxis range is constant. Lets say it is defined as MAX_RANGE seconds, and you want that once it passes MAX_RANGE seconds it will clear the graph and start over again from 0 sec.

If all this is right then I guess you already have a function that you are calling once every T seconds in order to update the plot. If not then take a look at this example.
Lets assume that you already have a function that you are calling every T seconds:

void MyPlot::updatePlot(int yValue)

Then simply add a timeCounter as a class variable that will be updated every call. Then add an if statement that will check if it passed MAX_RANGE. If it did then clear the graph using clearData(), add the new value and reset timeCounter. If it didn't then just add the new value. Simple example (just make the changes to fit for your case):

void MyPlot::updatePlot(int yValue){
    this->timeCounter += T;
    if (this->timeCounter >= MAX_RANGE) {
        ui->customPlot->graph(0)->clearData();
        ui->customPlot->graph(0)->addData(0, yValue);
        this->timeCounter = 0;
    }
    else {
        ui->customPlot->graph(0)->addData(this->timeCounter, yValue);
    }
}