How to delete rows where specific column value is not within other array?

Question

How can I delete rows in numpy 2d array where value in specific column is not within other array/list. Speed is important.

I found out how to keep only rows by conditioning column to specific value:

xyzv = xyzv[xyzv[:,3].astype(int) == 100]

But I need to compare it with way more values (array of my values). I just shoot into the dark:

xyzv = xyzv[xyzv[:,3].astype(int) in my_values]

And some other variations. But python didn't laugh.

Is xyzv a numpy 2d array ?wouldn't this xyzv[:,3].astype(int) == 100 give a boolean value ? And how could you pass a boolean value in here xyzv[boolean] ? — salil vishnu Kapur
– salil vishnu Kapur, Commented Jul 13, 2015 at 12:55

Divakar · Accepted Answer · 2015-07-13 13:03:06Z

1

You can use np.in1d -

search_nums = [100,102] # List of search numbers. NumPy arrays would work too.
xyzv = xyzv[np.in1d(xyzv[:,3].astype(int),search_nums)]

Sample run -

In [42]: xyzv = np.random.randint(98,104,(7,4)).astype(float)

In [43]: xyzv
Out[43]: 
array([[  98.,  100.,  102.,  102.],
       [  99.,  102.,  102.,  101.],
       [ 100.,   99.,   98.,  100.],
       [ 100.,  101.,  102.,   99.],
       [  99.,  102.,  103.,  101.],
       [ 103.,  100.,   98.,  102.],
       [ 102.,  101.,  103.,  101.]])

In [44]: search_nums = [100,102]

In [45]: xyzv[np.in1d(xyzv[:,3].astype(int),search_nums)]
Out[45]: 
array([[  98.,  100.,  102.,  102.],
       [ 100.,   99.,   98.,  100.],
       [ 103.,  100.,   98.,  102.]])

edited Jul 13, 2015 at 13:03

answered Jul 13, 2015 at 12:55

Divakar

222k19 gold badges273 silver badges374 bronze badges

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

1 Comment

Miro Over a year ago

Just small amendment, I asked to delete which is not in search_nums. Which in other words means keep what is in search_nums. So I deleted ~ to not invert it. Thank you.

Collectives™ on Stack Overflow

How to delete rows where specific column value is not within other array?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related