How to choose an analytical expression from a graph?

Question

Mathematics

Good afternoon.
I have the following task: "There is an electrical circuit. There is an input signal in the form of a graph, it is necessary to make an output signal." This is in short.
I have a graph:

With examples of input data in the form:

tначальная = -10 секунд
tконечное = 10 секунд
U = -50 В

And I need to write this graph as an analytical expression similar to (example!):

And to be precise, I also need to write a function that initializes the float array according to a given graph (in the form of an analytical expression).

Answer 1

Honestly, this is a 5th grade school problem.
Can't you formulate a straight line?
y=kx+b
You have two points, for example (tstart;0) and (0;U). We compose a system of equations, solve, we get the equation of a straight line.
More advanced sawtooth*rectangular functions can be used.
Initializing an array is even easier. You need to loop through x from -infinity to infinity (or other boundaries), substituting each x into your function and storing the resulting value, for example, in a list.