Table 4 Best equation obtained by PySR using R, where x₀, x₁, and x₂ represent lnΔK, R, and ln(1-ΔK_th/ΔK), respectively

1

0

\(- 16.64\)

3

0.506034

\(x_{0} - 18.65\)

4

1.015250

\(- \ln (\left| {x_{2} } \right|) - 17.52\)

5

5.138852

\({{ - 0.79} \mathord{\left/ {\vphantom {{ - 0.79} {x_{2} }}} \right. \kern-0pt} {x_{2} }} - 20.06\)

6

7.903765

\(- 2.78{ \times }\ln (\left| {x_{2} } \right|) - 19.08\)

8

1.355014

\(- 3.66{ \times }\ln (\left| {x_{2} } \right|) - x_{2} - 20.76\)

9

1.920022

\(3.97{ \times }x_{0} + 2.99{ \times }x_{1} - 24.82\)

10

1.063165

\(- 3.33{ \times }\ln (\left| {x_{2} } \right|) - 0.62{ \times }x_{2} - 20.12\)

11

1.196781

\(\ln (\left| {x_{2} } \right|){ \times ((} - 0.31{ \times }\ln (\left| {x_{2} } \right|)) + 2.38) - 19.44\)

12

1.579150

\(1.65{ \times }\left( {x_{0} - \ln (\left| {x_{2} } \right|)} \right) + 1.12{ \times }x_{1} - 18.17\)

14

1.431851

\(2.59{ \times }x_{0} + 1.87{ \times }x_{1} - 1.03{ \times }\ln (\left| {x_{2} } \right|) - 22.85\)

16

0.160530

\(2.61{ \times }x_{0} + x_{1} + x_{1} - {{0.02} \mathord{\left/ {\vphantom {{0.02} {x_{1} }}} \right. \kern-0pt} {x_{1} }} - \ln (\left| {x_{2} } \right|) - 22.85\)

17

0.002519

\(2.62{ \times }x_{0} + x_{1} + x_{1} + 0.10{ \times }\ln (\left| {x_{1} } \right|) - \ln (\left| {x_{2} } \right|) - 22.83\)

18

0.565648

\(2.67{ \times }x_{0} + {{0.16} \mathord{\left/ {\vphantom {{0.16} {x_{0} }}} \right. \kern-0pt} {x_{0} }} + 1.88{ \times }x_{1} - \ln (\left| {x_{2} } \right|) + 0.44 - 22.69\)

20

0.048846

\(2.69{ \times }x_{0} + {{0.13} \mathord{\left/ {\vphantom {{0.13} {x_{0} }}} \right. \kern-0pt} {x_{0} }} + x_{1} + x_{1} - {{0.02} \mathord{\left/ {\vphantom {{0.02} {x_{1} }}} \right. \kern-0pt} {x_{1} }} - \ln (\left| {x_{2} } \right|) - 23.11\)