What is BatViz?
BatViz is a measure of how difficult Test match batting conditions are at the moment. The higher the reading on the BatViz indicator, the more difficult it is for the batsmen to survive and score.
How does it work?
BatViz analyses the ball tracking data from the most recent balls bowled and evaluates each of them based on six criteria – speed, length, line, bounce, movement in the air, and movement off the pitch. It then combines these scores for the most recent 50 balls bowled and gives you an average difficulty rating.
Can you explain more about how it works?
BatViz performs something called a nearest neighbour analysis. We have a database containing all the information from over 300,000 past balls bowled in Test cricket. Each time a ball is bowled in the match we compare this current ball’s data with those in the database and find the 1,000 balls which are most similar in our six criteria – speed, length, line, bounce, movement in the air, and movement off the pitch. We then look at the outcomes from those 1,000 near identical past balls and use them to grade the difficulty of the current ball.
Let’s say that our 1,000 near identical balls went for 450 runs, and took 10 wickets. Then we estimate that the current ball would average 45 in Test cricket, would go for 0.45 runs and take a wicket 1% of the time. That average is higher than Test cricket in general, so this would be a moderately easy ball to face.
We do this for each ball bowled. Then we combine the scores for the most recent 50 balls (divided into fast and slow bowlers) and determine how difficult they should have been for the batsman. Let’s say that the combined totals for our 50 balls show that they would have gone for 21 runs and would have taken 1.4 wickets. Then our predicted average for those 50 balls would be 21/1.4 = 15, and so the difficulty rating for that period would be very high.