Animator in Script

Once the Animator Component is setup, you can control the parameters via script.

The parameters can be set in the Animator controller. Anything in "Quotes" is what you wrote down as a variable there.

[SerializeField] private Animator anim;

Drag the GameObject in the scene view into the "Anim" field.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.InputSystem;

public class PlayerController : MonoBehaviour
{
    private Vector2 movementInput;
    [SerializeField] private float MOVESPEED = 4.0f;
    private Rigidbody2D rb;

    [SerializeField] private Animator anim;


    private void Awake()
    {
        rb = GetComponent<Rigidbody2D>();
    }


    public void OnMove(InputAction.CallbackContext ctx)
    {
        movementInput = ctx.ReadValue<Vector2>();

        if (movementInput.x == 1 || movementInput.x == -1 || movementInput.y == 1 || movementInput.y == -1)
        {
            anim.SetFloat("lastMoveX", movementInput.x);
            anim.SetFloat("lastMoveY", movementInput.y);
        }
    }

    private void FixedUpdate()
    {
        //Moving the character
        rb.velocity = movementInput * (MOVESPEED * Time.fixedDeltaTime);

        //Animator Controls, make sure the quotations match the parameter names in the Animator controller
        anim.SetFloat("moveX", rb.velocity.x);
        anim.SetFloat("moveY", rb.velocity.y);
    }
}

Getting the direction of the look is something I'm thinking about. One thing that doesn't throw an error is this:

Debug.Log(anim.GetFloat("lastMoveX"));