From kyousan at sina.com  Wed Jun 20 04:26:13 2007
From: kyousan at sina.com (kyousan at sina.com)
Date: Wed, 20 Jun 2007 04:26:13 +0200 (CEST)
Subject: [Rd] Error in funcion distancia() in package dprep(v1.0) (PR#9745)
Message-ID: <20070620022613.67EA548497@slim.kubism.ku.dk>

Full_Name: Kang Yousan
Version: 2.5.0
OS: Windows XP
Submission from: (NULL) (211.137.211.67)


There is a bug in function distancia() in package dprep. See the description
below.

> distancia

1 function (x, y) 
2 {
3      if (class(y) == "matrix") {
4          distancia = drop(sqrt(colSums((x - t(y))^2)))
5          distancia = t(distancia)
6      }
7      else distancia = sqrt(sum((x - y)^2))
8      distancia
9  }

The t(y) in line 4 should be modified to y. Before the change, see example:
> (x=rnorm(4))
[1]  0.02670846  1.24512505 -0.22145290  1.99760521
> (y=matrix(rnorm(12),4,3))
           [,1]       [,2]       [,3]
[1,]  0.4181184  1.8980350 -1.7398861
[2,] -0.1906483 -0.1777747  0.6666913
[3,]  0.2239468 -0.2631944 -0.3586917
[4,] -1.0316230 -0.7121346  0.3587542
> distancia(x,y)
         [,1]     [,2]     [,3]     [,4]
[1,] 1.698568 2.272631 2.336264 2.847838

After the change:
a<-function (x, y) 
{
    if (class(y) == "matrix") {
        distancia = drop(sqrt(colSums((x - y)^2)))
        distancia = t(distancia)
    }
    else distancia = sqrt(sum((x - y)^2))
    distancia
}
> a(x,y)
         [,1]     [,2]     [,3]
[1,] 3.404299 3.587609 2.481957

The latter result is resonable according to the description of the function
return value: "distancia numeric value representing the Euclidean distance
between x and y, or a row matrix representing the Euclidean distance between x
and each column of y."

Thanks for attention.



[Rd] Error in funcion distancia() in package dprep(v1.0) (PR#9745)
kyousan at sina.com