[R] How to select a whole column? Thanks!

[Jinsong Zhao]

Dear all,

I hope to remove a whole column from a data frame or matrix (> 2000
columns). All value in the column are same. The first thing is to
select those columns. 

For instance, I hope to remove the V3~6 column, for all the value in
those colume is zero.

  V3 V4 V5 V6     V7     V8     V9    V10
1  0  0  0  0  0.000  0.000  0.000  0.000
2  0  0  0  0  0.000  0.000  0.000  0.000
3  0  0  0  0  0.000  0.000  0.000  0.000
4  0  0  0  0  0.000  0.000  0.000  0.000
5  0  0  0  0  0.000  0.000  0.000  0.000
6  0  0  0  0 -0.001 -0.001 -0.001 -0.001
7  0  0  0  0  0.000  0.000  0.000 -0.001
8  0  0  0  0  0.000  0.000  0.000 -0.001
9  0  0  0  0 -0.009 -0.012 -0.015 -0.018

I mean how to select the first four columns.

Thank you very much for your consideration on this matter.

Best wishes,

Jinsong

=====
(Mr.) Jinsong Zhao
Ph.D. Candidate
School of the Environment
Nanjing University
22 Hankou Road, Nanjing 210093
P.R. China
E-mail: jinsong_zh at yahoo.com