Python DataFrame Apply conditions to row and column

Question

I have a python dataframe which contains measurements, including positions.

I need to calculate the angle of the direction, which is done by ATAN(Y/X).

However, I need to add the condition of the sign of X and Y to account for the direction of the angle (which quadrant we are in).

So, I want to know how I can run through every row in the dataframe and for the column 'X'and 'Y' I need to : If X is positive and Y is positive then.. If X is positive and Y is negative then.. If X is negative and Y is positive then.. If X is negative and Y is negative then..

I am struggling being able to apply this logic to a dataframe.

Anyone got an idea of how to solve this problem?

busybear · Accepted Answer · 2019-02-05 02:31:51Z

2

Even easier is to use np.arctan2. This will take into account the sign of your two sides to give you an angle in [-pi, pi].

To answer your actual question, you can use a nested if statements for instance:

if x >= 0:
     if y >= 0:
         # code
     else:  # y < 0
         # code
else:  # x < 0
     if y >= 0:
         # code
     else:  # y < 0
         # code

edited Feb 5, 2019 at 2:31

answered Feb 5, 2019 at 2:26

busybear

10.7k1 gold badge29 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

gmds · Accepted Answer · 2019-02-05 02:28:09Z

0

Instead of including such logic manually, you might want to consider using the arctan2 function from numpy; you can find the documentation here. It handles the sign of the coordinates passed to it automatically.

In this case, assuming your columns in the DataFrame are named X and Y and the DataFrame is itself named df, you could just do np.arctan2(df['Y'], df['X']).

answered Feb 5, 2019 at 2:28

gmds

20k4 gold badges37 silver badges65 bronze badges

1 Comment

Kakemonster Over a year ago

Yes, such an elegant and easy solution! Thanks

Collectives™ on Stack Overflow

Python DataFrame Apply conditions to row and column

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related