Time varying function on LTspice

[Firenze02]

Hi,

I would like to create a variable resistor as shown in the attached pictures.
How can I create a variable resistor depending on the value of current?

I saw the following tutorial, but I don't know hot to replicate my function (where some parameters change during the time but not varyin current).

Is it possible in LTspice?

Thank you.

 

[Firenze02]

Thank you.

I would have a further question.

How can I change alfa1, alfa2, alfa3 depending on the value of i(r1)?

 

[alec_t]

My edit to post #2 didn't upload.
Here's an example for varying resistance on the fly, as a function of current. The expression for R would need to be much more complex (more 'if' clauses) to handle the various alapha values :