7.2.3 Can you answer these questions?

7.2.3.1 NDSolve - interpolation or machine precision problem

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=237920

For the following equations; 
$$\begin{align} 
\frac{\partial \text{NN}(t)}{\partial t}&=-\frac{(c \times\text{Sigma})}{\pi\times  L\times \text{Omega}^2} \text{NN}(t) \times\text{Phi}(t)-\frac{\... 
[plotting] [differential-equations] [equation-solving] [warning-messages]
 

asked by confused https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74890 1 vote

7.2.3.2 Matrix regularization, how to pick $\lambda$

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=237834

Since v12  FindFit[]  now supports regularisation, such as  Tikhonov regularization. Do there exist statistics to help guide the choice of the hyper-parameter $\... 
[probability-or-statistics] [fitting] [linear-algebra]
 

asked by Tomi https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36939 2 votes

7.2.3.3 Memory consuming Expand

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=238106

 Expand   floods all my 64GB RAM in MMA 12.1 (Windows). Therefore I cannot run the code. Somebody with >64GB RAM could give the result. A memory saving alternative ... 
[series-expansion] [memory]
 

asked by granular bastard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=69288 1 vote