When you teach people, you learn!
Look at things in a different way, from another perspective. And you become much more efficient!
The most efficient way to do an ifelse ala Excel:
In R, it would be:
df$X <- if(df$A == "-1"){-df$X}else{df$X}
In Python, it would be:
import numpy as np
np.where(df['A'] < 1, -df['X'], df['X'])
check the full post out at stackoverflow: https://stackoverflow.com/questions/43711020/python-version-of-rs-ifelse-statement/43711056#43711056