Message-ID: <13E5504DD4AE454AAD151A4D239FBE5E010B00F3@parpaioun.aix.cemagref.fr>
Date: 2008-12-24T13:28:01Z
From: Veslot Jacques
Subject: selecting a subset of a matrix based on a value occurring in 5 records
In-Reply-To: <20081224121730.E0D3D595608@borg.st.net.au>
> mat[,colSums(mat!=0)>=5]
Jacques VESLOT
CEMAGREF - UR Hydrobiologie
Route de C?zanne - CS 40061
13182 AIX-EN-PROVENCE Cedex 5, France
T?l. + 0033 04 42 66 99 76
fax + 0033 04 42 66 99 34
email jacques.veslot at cemagref.fr
>-----Message d'origine-----
>De?: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] De la part
>de Bob Green
>Envoy??: mercredi 24 d?cembre 2008 13:17
>??: r-help at r-project.org
>Objet?: [R] selecting a subset of a matrix based on a value occurring in 5 records
>
>
>Hello,
>
>>I am hoping for some advice as to how I might create a subset of a
>>matrix. The matrix is 176 x 3530. The rows are individual records
>>and the columns words. I want to create a new matrix that only
>>consists of words which occur in at least 5 records. For example,
>>if column 7 is "charges" and this only appears in 4 records/rows
>>this variable would not be included, whereas if column 109 was the
>>word "monitor" and occurred in 95 records it would be saved into the
>>new matrix. Values in the matrix are numbers, such that if a word
>>does not occur in a record the cell contains a zero, whereas if it
>>occurs 7 times there is a value of 7 for that record. It is the
>>number of records rather than the than the column total that is the
>>criteria for determing inclusion into the matrix.
>
>
>Any suggestions on how I might reduce the size of this matrix so as
>to include only those columns in which a word occurs at least in 5
>records is much appreciated,
>
>regards
>
>Bob
>
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