What is the inverse of numpy's log1p()?

Question

I transformed my data with:

Y = np.log1p(Y)

What is the formula to transform the values back to the natural values?

back  = np.e**Y

This did not work.

Answer 1

You can use numpy.expm1() which is the inverse of numpy.log1p()

import numpy as np
Y = np.log1p(Y)
back = np.expm1(Y)