I have a geodata frame. I have a column and I would like to create a new one subtracting one if that column is strictly greater than 0, otherwise, maintain the same value.
I have tried the following:
df['new_column'] = df.apply(lambda y: (df['old_column'].subtract(1)) if y['old_column'] > 0 else y['old_column'], axis=1)
It's doing well at the time to differentiate when old_column is greater than 0, but at the moment to substract one, it's doing something strange, it's not substracting, it's just given a series of numbers, 3-2 2-1 1 1-1, things like that. Why is it doing that?
The error is that you need to take one cell and not the entire column df['old_column'] => y['old_column']. In addition, there is no subtract method for a numpy object.
df['new_column'] = df.apply(lambda y: (y['old_column'] - 1) if y['old_column'] > 0 else y['old_column'], axis=1)
A simpler expression if data from one column is used
df['new_column'] = df['old_column'].apply(lambda y: y - 1 if y > 0 else y)