Hi
How Many Hours of Study Before You Can Reach a Certain Elo

Hey, I'm new here, just exploring the site. I wanted to ask: How did you come up with this formula/expression?

From the Article How Many Hours Of Chess Study Does It Take To Be A Grandmaster? By NM SmarterChess
I saw a graph like this
I noticed that the graph is kinda similar to a natural logarithm graph
The following graph confirms it.
Then I manipulate the equation.
First, we will find the comparison between number of hours of study and the natural logarithm graph.
I assigned the value 4 as synonymous to the number of hours Nakamura spent before achieving grandmaster title which is (14-7.5) *20 *52 which is 6760
But as we approach x, we approach negative infinity, so I selected 0.1 because it has the right value that fits the graph which is -2.3
Then, the number of hours, xi = k * ( x - 0.1)
Substitute: xi = 6760 and x = 4
We find k = 1733
Then, xi = 1733 * ( x - 0.1 )
Next, we will find the comparison between Elo and the natural logarithm graph.
y = ln(x)
Then we found that the lower limit of y is -2.3, so
yi = k *( y + 2.3 )
We plug in yi = 2500 and y = ln(4) which is 1.386
We find k = 678
Then we manipulate the equations
x = xi / 1733 + 0.1 and y = yi / 678 -2.3
We plug in both equations:
yi / 678 - 2.3 = ln (xi / 1733 + 0.1)
Since we want to know the number of hours to study to reach a certain elo, we separate xi to the left by manipulating the equation
exp ( yi / 678 - 2.3 ) = xi / 1733 + 0.1
xi = 1733 ( exp ( yi / 678 - 2.3 ) - 0.1 )
Simplify,
xi = 1733 ( exp ( ( yi - 1559.4 ) / 678 ) - 173.3
y = 1733 ( exp ( ( x - 1559.4 ) / 678 ) - 173.3
How Many Hours of Study Before You Can Reach a Certain Elo
Formula: y = 1733 exp ( ( x -1559.4 ) / 678 ) - 173.3
Where: y is the number of hours of study and x is the Elo rating