Re: selecting columns from a list
- To: mathgroup at smc.vnet.net
- Subject: [mg47874] Re: selecting columns from a list
- From: "Curt Fischer" <crf3 at po.cwru.edu>
- Date: Thu, 29 Apr 2004 03:05:56 -0400 (EDT)
- References: <c6o4pc$clk$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Edo wrote:
> Hello
> I just started with mathematica, wanted to load a comma separated data
> file and drop the first two columns. So I did
> data=Import["C:\Data\filename.ext","CSV"]; to get the file into a
> variable "data", then I am stuck, after doing some reading in the help
> files about Drop, Partition, Take. ・瘢雹etc
> could someone tell me what to read and where to find info about
> indexing different data structures
It's all there in the Help Browser. Look at the help for Part[].
Here's some simple ways of doing what you want.
In[1]:=
a={{1,2,3,4},{11,22,33,44},{111,222,333,444}}
Out[1]=
{{1,2,3,4},{11,22,33,44},{111,222,333,444}}
Use a replacement rule:
In[2]:=
a/.{x_,y_,z_,w_}\[Rule] {z,w}
Out[2]=
{{3,4},{33,44},{333,444}}
Or use Part[]:
In[3]:=
a[[All,{3,4}]]
Out[3]=
{{3,4},{33,44},{333,444}}
--
cf