Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
594 views
in Technique[技术] by (71.8m points)

python - Filter a 2D numpy array

I want to have a sub array (between min and max) of a numpy 2D ndarray

    xy_dat = get_xydata()
    x_displayed = xy_dat[((xy_dat > min) & (xy_dat < max))]

min and max are float in order to be compare with the first value of the array xy_dat

xy_dat is a 2D numpy array :

[[ 735964.            1020.        ]
 [ 735964.04166667    1020.        ]
 [ 735964.08333333    1020.        ]
 ..., 
 [ 736613.39722222    1095.        ]
 [ 736613.40416667    1100.        ]
 [ 736613.41111111    1105.        ]]

x_displayed is correctly filtered but I have lost the second value (it is now a 1D array) :

[ 735964.04166667  735964.08333333  735964.125      
 ...,  
736613.39027778  736613.39722222  736613.40416667]

How make the filter on the first value and keep the other ?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

You should perform the condition only over the first column:

x_displayed = xy_dat[((xy_dat[:,0] > min) & (xy_dat[:,0] < max))]

What we do here is constructing a view where we only take into account the first column with xy_dat[:,0]. By now checking if this 1d is between bounds, we construct a 1D boolean array of the rows we should retain, and now we make a selection of these rows by using it as item in the xy_dat[..] parameter.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

1.4m articles

1.4m replys

5 comments

57.0k users

...