I have some question about variable domain.
I created a Date driven PCE model, of which x1 was set as shown in Fig.1.
Because it was assumed to be a uniform distribution, the polynomial follows the Legendre polynomial, and the scale of the variable is rescaled from [-1, 3] to [-1, 1].
In this case, Fig.4. According to the equations of Fig.2. and Fig.3.
I also confirmed that the variables were converted.
However, when the variable was directly converted using the equation in Fig. 4, the value was slightly different. (Fig.5.)
Is the expression I used wrong? why the value is different?