Plot real time values in Viewport

Can you please elaborate on what real-time is in the context of your project?

You can certainly use a for() loop to generate this within one frame of the draw() cycle.

I combined these to generate data and plot it:
redraw() / Reference / Processing.org
thread() / Reference / Processing.org

An example that generates data in the background and updates sketch window every 1000ms:

int x, y;

void setup() 
  {
  size(200, 200, P2D);
  thread("requestData");
  noLoop();
  }

void draw()
  {
  fill(random(256));  
  circle(x, y, 20);
  
  // You can write code here to plot data
  
  }

// Runs in background thread and updates x and y every 1000ms
void requestData() 
  {
  while(true)
    {
    x = random(width);
    y = random(height);
    delay(1000);
    redraw();
    }
  }

I often simulate incoming data from other sources with the example above.

:)