Is Poker Copilot’s Bankroll Chart Accurate?

Loyal Poker Copilot customer Jon noticed that his bankroll chart showed his winnings to be a couple of dollars less than they are, until he zoomed in.

Here’s my explanation:

The problem is caused by trying to plot, say, 100,000 data points (the number of hands played) onto a screen with a resolution of roughly 1000 horizontal pixels. Each actually charted point must represent roughly 100 data points (assuming no sub-pixel rendering). So the chart is plotted by sampling the data. Unfortunately this results in a loss of accuracy.

This is not just a problem for Poker Copilot, but for any charting software that must show more data points than the screen’s resolution can handle. The more volatility in the data, the greater the visual errors, until you zoom in. All the chart can do is show the general trend. In sampling, outlying points sometimes don’t get handled well.

As you continue to get more hands, you’ll find at certain times, the outliers will be shown, and at other times they won’t.

Knowing that many of my most supportive customers are also damn good at mathematics and statistics, I thought I would post this explanation publicly, in case there are any glaring errors in this explanation.