Re: Help! Delete Casses based on column

• To: mathgroup at smc.vnet.net
• Subject: [mg58306] Re: Help! Delete Casses based on column
• Date: Sun, 26 Jun 2005 23:13:09 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```On 6/26/05 at 1:33 AM, tornado78 at hotmail.com (tornado78) wrote:

>I need to take a large numeric matrix and remove all the rows that
>have a value less than X in column N

First, using Table to generate a random matrix

In[1]:=
data = Table[Random[], {i, 5}, {j, 5}]
Out[1]=
{{0.7782881593866494,
0.6753591418097964,
0.9449449797796714,
0.37735570973406635,
0.6250430512630213},
{0.7774244995727889,
0.6447847938619459,
0.8176979735737523,
0.8623853364999774,
0.0803196694199144},
{0.8740035700727821,
0.402979840643203,
0.46652340639843337,
0.8909105854301345,
0.3997272322978968},
{0.6150459139286458,
0.5304020309232242,
0.12667830628081253,
0.6939192674223005,
0.8949467718141887},
{0.44714646243832995,
0.17821492267582964,
0.5725611138098228,
0.3112823655223339,
0.6688583030516806}}

Then Pick can be used to do what you want. That is dropping all of the rows which have a value of less than .5 in column 4 could be done as:

In[2]:=
Pick[data, (#1 >= 0.5 & ) /@  data[[All,4]]]
Out[2]=
{{0.7774244995727889,
0.6447847938619459,
0.8176979735737523,
0.8623853364999774,
0.0803196694199144},
{0.8740035700727821,
0.402979840643203,
0.46652340639843337,
0.8909105854301345,
0.3997272322978968},
{0.6150459139286458,
0.5304020309232242,
0.12667830628081253,
0.6939192674223005,
0.8949467718141887}}
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```

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