java - how to simulate an ECG (electro-cardiogram)

Question

I am working on some kind of project which involves simulating an ECG (electrocardiogram). I do it by generating some random numbers between an interval and sending that data to another program analyzing and graphing it. But, the problem is the random number generated between an interval say [a,b] by java code have a lot of variance, meaning the next generated random value differs greatly from the previous number. What I want is a flow of random numbers varying slightly so that graph looks smooth. At this point, the graph generated is very spiky, but I want it to be smooth and varying like a real ECG graph.

Please help me do that.

Here is the code

//setup ECG graph
        StdDraw.setXscale(0.0, 100.0);
        StdDraw.setYscale(0.0,200.0); 
        StdDraw.setPenColor(StdDraw.BLUE); 
        StdDraw.setPenRadius(0.0009);
        //generate random points between interval of range
        int t = 0; 

        int prevVal = 0; 
        int nextVal; 
        while(true){

            nextVal = range.getRandomValue(); 
            System.out.println(nextVal);

            StdDraw.point(prevVal, nextVal);
            StdDraw.line(t-1, prevVal, t, nextVal);

            StdDraw.show(100);

            prevVal = nextVal; 
            t = (t+1) % 100;
            if(t == 0){
                StdDraw.clear(); 

            }
        }

Thank You

Answer 1

Why don´t you try modulating your random signal with a sin(t) function:

long n = 0; 

double randomWeight = 0.5;

while(true) {

    nextVal = range.getRandomValue(); 

    double temp = AMPLITUDE*(randomWeight*((double)nextVal)+(1.0-randomWeight)*Math.sin(2.0*Math.PI*((double)n)*WIDTH_FACTOR));


    nextVal = (long)temp; 

    n++;

    System.out.println(nextVal);

    StdDraw.point(prevVal, nextVal);
    StdDraw.line(t-1, prevVal, t, nextVal);

    StdDraw.show(100);

    prevVal = nextVal; 
    t = (t+1) % 100;
    if(t == 0){
        StdDraw.clear(); 

}

The idea is to generate a sinusoidal wave function and add some random noise to it. You may want to add this noise to a square wave instead. I don´t really know very much about how an electrocardigram looks like but I suppose it must be governed by the heartbeat.

EDIT:

I have just checked how these signals look like:

It seems to me, a more accurate model would be given by a relatively flat random signal interrupted by periodic spikes:

long n = 0; 

while(true) {

    nextVal = range.getRandomValue(); 
    if(n % SPIKE_PERIOD == 0) nextVal = SPIKE_APLITUDE*nextVal;

    n++;


    System.out.println(nextVal);

    StdDraw.point(prevVal, nextVal);
    StdDraw.line(t-1, prevVal, t, nextVal);

    StdDraw.show(100);

    prevVal = nextVal; 
    t = (t+1) % 100;
    if(t == 0){
        StdDraw.clear(); 

}