Updating Pandas DataFrame column conditionally using other columns

Question

With a DataFrame like the one below, how do I set c1len equal to zero when c1pos equals zero? I would then like to do the same for c2len/c2pos. Is there an easy way to do it without creating a bunch of columns to arrive at the desired answer?

             distance  c1pos  c1len  c2pos  c2len  daysago
 line_date                                                
 2013-06-22      7.00      9    0.0      9    6.4       27
 2013-05-18      8.50      6    4.6      7    4.9       62
 2012-12-31      8.32      5    4.6      5    2.1      200
 2012-12-01      8.00      7    7.1      6    8.6      230
 2012-11-03      7.00      7    0.0      7    2.7      258
 2012-10-15      7.00      7    0.0      8    5.2      277
 2012-09-22      8.32     10   10.1      8    4.1      300
 2012-09-15      9.00     10   12.5      9   12.1      307
 2012-08-18      7.00      8    0.0      8    9.2      335
 2012-08-02      9.00      5    3.5      5    2.2      351
 2012-07-14     12.00      3    4.5      3    3.5      370
 2012-06-16      8.32      7    3.7      7    5.1      398

Jeff · Accepted Answer · 2013-08-23 20:24:24Z

6

I do't think you have anything that actually satifies those conditions, but this will work

This creates a boolean mask for when the rows of the column in question (e.g. c2pos) are 0; then it is setting the column c2len to 0 for those that are True

In [15]: df.loc[df.c2pos==0,'c2len'] = 0

In [16]: df.loc[df.c1pos==0,'c1len'] = 0

In [17]: df
Out[17]: 
            distance  c1pos  c1len  c2pos  c2len  daysago
2013-06-22      7.00      9    0.0      9    6.4       27
2013-05-18      8.50      6    4.6      7    4.9       62
2012-12-31      8.32      5    4.6      5    2.1      200
2012-12-01      8.00      7    7.1      6    8.6      230
2012-11-03      7.00      7    0.0      7    2.7      258
2012-10-15      7.00      7    0.0      8    5.2      277
2012-09-22      8.32     10   10.1      8    4.1      300
2012-09-15      9.00     10   12.5      9   12.1      307
2012-08-18      7.00      8    0.0      8    9.2      335
2012-08-02      9.00      5    3.5      5    2.2      351
2012-07-14     12.00      3    4.5      3    3.5      370
2012-06-16      8.32      7    3.7      7    5.1      398

answered Aug 23, 2013 at 20:24

Jeff

130k21 gold badges223 silver badges189 bronze badges

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

2 Comments

TravisVOX Over a year ago

Perfect. I didn't realize the sample given didn't have any qualifying rows. The actual frame is hundreds of rows... thank you!!

Jeff Over a year ago

gr8, extensive documentation here

Collectives™ on Stack Overflow

Updating Pandas DataFrame column conditionally using other columns

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related