[R] identify extremes positions of values into matrix
Francisco J. Zagmutt
gerifalte28 at hotmail.com
Fri Nov 3 19:48:57 CET 2006
Oi Milton,
Is this what you are after?
x=read.table("miltondat.txt")
>x
V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
1 0 0 0 0 0 0 0 0 0 0
2 0 0 0 0 0 1 1 1 0 0
3 0 0 0 0 0 1 1 1 0 0
4 0 0 0 0 0 0 0 0 0 0
5 0 0 2 2 2 0 0 0 0 0
6 0 0 0 2 2 2 0 0 0 0
7 0 0 2 2 2 2 2 2 0 0
8 0 0 0 0 0 0 0 0 0 0
idx=which(x==2,arr.ind=T) #Index of observations with values == 2 . Notice
the use of arr.ind=t to get the rows and columns of the observations
>idx
row col
5 5 3
7 7 3
5 5 4
6 6 4
7 7 4
5 5 5
6 6 5
7 7 5
6 6 6
7 7 6
7 7 7
7 7 8
>range(idx[,"row"]) #gives you the min and max of the rows with x==2
[1] 5 7
>range(idx[,"col"])#gives you the min and max of the columns with x==2
[1] 3 8
You can refine this and wrap it in a function to make reports in a more
suitable form
Regards
Francisco
Dr. Francisco J. Zagmutt
College of Veterinary Medicine and Biomedical Sciences
Colorado State University
>From: Milton Cezar Ribeiro <milton_ruser at yahoo.com.br>
>To: r-help at stat.math.ethz.ch
>Subject: [R] identify extremes positions of values into matrix
>Date: Fri, 3 Nov 2006 11:25:32 -0300 (ART)
>
>Hi R-friends around world!
> I have a matrix that looks like bellow one.
>Each cell are filled with values 0, 1 or 2.
>In fact I have a lot of 512x512 matrices, with
>values varying from 0 to 999.
> I need to retrieve the left and right columns
>and the top and botton lines of the matrix
>where occours for example the value 2.
>Column and row labels are included at the example.
>
> 1234567890
>1 0000000000
>2 0000011100
>3 0000011100
>4 0000000000
>5 0022200000
>6 0002220000
>7 0022222200
>8 0000000000
>
> At this example, the right answer are:
> collumns 3 and 8
> lines 5 and 7
> Any idea of how can I solve this?
> Kind regards,
> Miltinho
>
>
>---------------------------------
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