# [R] (second round) creating a certain type of matrix

From: Taka Matzmoto <sell_mirage_ne_at_hotmail.com>
Date: Wed 08 Feb 2006 - 04:03:14 EST

Hi R users
Here is what I got with help from Petr Pikal (Thanks Petr Pikal). I modified Petr Pikal's code to a little
to meet my purpose.

I created a function to generate a matrix

generate.matrix<-function(n.variable)
{
mat<-matrix(0,n.variable,(n.variable/2)/5+1) #matrix of zeroes dd<-dim(mat) # actual dimensions
mat[1:(dd/2),1]<-1 #put 1 in first half of first column mat[((dd/2)+1):dd,1]<-rnorm(dd/2,0,1) #put random numbers in following part of the matrix column 1
mat[((dd/2)+1):((dd/2)+5),2]<-rnorm(5,0,1) #put random numbers in column2
for (i in 3:(dd))

{

```        length.of.rand.numbers <- 5
my.rand.num<- rnorm(length.of.rand.numbers, 0,1)
start <- dd/2+5*(i-2)+1
end <- start + length.of.rand.numbers-1
mat[((start):end), i]<- my.rand.num
```
}
mat
}

Do you (any R users) have any suggestion to this function to make this function work better or efficiently?

Taka
It works but I

>From: "Petr Pikal" <petr.pikal@precheza.cz>
>To: "Taka Matzmoto" <sell_mirage_ne@hotmail.com>,r-help@stat.math.ethz.ch
>Subject: Re: [R] creating a certain type of matrix
>Date: Tue, 07 Feb 2006 08:58:59 +0100
>MIME-Version: 1.0
>bay0-mc8-f13.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.211); Mon, 6
>Feb 2006 23:59:02 -0800
>Received: from localhost (localhost [127.0.0.1])by mail.precheza.cz
>(Mailer) with ESMTP id A636C34E584;Tue, 7 Feb 2006 08:59:00 +0100 (CET)
>Received: from mail.precheza.cz ([127.0.0.1])by localhost (mail.precheza.cz
>[127.0.0.1]) (amavisd-new, port 10024)with LMTP id 28608-02-30; Tue, 7 Feb
>2006 08:58:59 +0100 (CET)
>mail.precheza.cz (Mailer) with ESMTP id 35E8634E582;Tue, 7 Feb 2006
>08:58:59 +0100 (CET)
>Received: from pikal ([192.168.210.65]) by n1en1.precheza.cz
>(Lotus Domino Release 6.5.4FP2) with ESMTP id 2006020708585800-252
>; Tue, 7 Feb 2006 08:58:58 +0100 X-Message-Info:
>JGTYoYF78jEHjJx36Oi8+Z3TmmkSEdPtfpLB7P/ybN8=
>X-pmrqc: 1
>Return-Receipt-To: "Petr Pikal" <petr.pikal@precheza.cz>
>Priority: normal
>X-mailer: Pegasus Mail for Windows (4.21c)
>X-MIMETrack: Itemize by SMTP Server on SRVDomino/PRECHEZA(Release 6.5.4FP2
>| September 26, 2005) at 07.02.2006 08:58:58,Serialize by Router on
>SRVDomino/PRECHEZA(Release 6.5.4FP2 | September 26, 2005) at 07.02.2006
>08:58:58,Serialize complete at 07.02.2006 08:58:58
>X-Virus-Scanned: by amavisd-new-20030616-p10 (Debian) at precheza.cz
>Return-Path: petr.pikal@precheza.cz
>X-OriginalArrivalTime: 07 Feb 2006 07:59:03.0289 (UTC)
>FILETIME=[5C87D690:01C62BBC]
>
>Hi
>
>as only you know perfectly which halves and other portions of your
>matrices contain zeroes and which contain random numbers you has to
>finalize the function yourself.
>Here are few ideas.
>
>n<-20
>mat<-matrix(0,n,(n/2)/5+1) #matrix of zeroes
>dd<-dim(mat) # actual dimensions
>mat[1:(dd/2),1]<-1 #put 1 in first half of first column
>mat[((dd/2)+1):dd,1]<-rnorm(dd/2,0,1) #put random numbers in
>following part of the matrix column 1
>mat[((dd/2)+1):(dd/2)+dd/4,2]<-rnorm(dd/4,0,1) #put
>random numbers in column2
>
>than according to n and dd values you can put any numbers anywhere in
>your matrix e.g. in for loop (not.tested :-)
>
>for (i in 3:dd) {
>
>arrange everything into following desired columns
>e.g.
>
>length.of.rand.numbers <- (i-2)*5
>my.rand.num<- rnorm(length.of.rand.numbers, 0,1)
>start <- dd/2+dd/4
>end <- start + length.of.rand.numbers
>mat[start:end, i]<- my.rand.num
>
>}
>
>HTH
>Petr
>
>On 7 Feb 2006 at 0:07, Taka Matzmoto wrote:
>
>From: "Taka Matzmoto" <sell_mirage_ne@hotmail.com>
>To: r-help@stat.math.ethz.ch
>Date sent: Tue, 07 Feb 2006 00:07:11 -0600
>Subject: [R] creating a certain type of matrix
>
> > Hi R users
> >
> > I like to generate a certain type of matrix.
> > If there are 10 variables, the matrix will have nrow=10,
> > ncol=((10/2))/5+1. so the resulting matrix's dimension 10 by 2. If
> > there are 50 variables the dimension of the resulting matrix will be
> > 50 by 6.
> >
> > The arrangement of elements of this matrix is important to me and I
> > can't figure out how to arrange elements.
> >
> > If I have 20 variables. The resulting matrix will be 20 by 3
> > The first half of first column of the matrix will be 1s. The all
> > elements on the second half of the first column of the matrix will be
> > random numbers coming from rnorm(1,0,1). The first half of the second
> > column of the matrix will be zeros. The first five elements of the
> > second half of the second column of the matrix will be random numbers
> > coming from rnorm(1,0,1). After that, the remaining elements of the
> > second half will be zeros. The first half of the third column of the
> > matrix will be zeors. The first five elements of the second half of
> > the third column will be zeros too and then 5 random numbers coming
> > from rnorm(1,0,1).
> >
> > If there are 40 variables the resulting matrix will be 40*5
> > The first half of first column of the matrix will be 1s. The all
> > elements on the second half of the first column of the matrix will be
> > random numbers coming from rnorm(1,0,1).
> >
> > The first half of the second column of the matrix will be zeros. The
> > first five elements of the second half of the second column of the
> > matrix will be random numbers coming from rnorm(1,0,1). After that,
> > the remaining elements of the second half will be zeros.
> >
> > The first half of the third column of the matrix will be zeors. The
> > first FIVE elements of the second half of the third column will be
> > zeros too and then 5 random numbers coming from rnorm(1,0,1) and then
> > the rest of elements of the third column will be zeros.
> >
> > The first half of the fourth column of the matrix will be zeors.The
> > first TEN elements of the second half of the fourth column will be
> > zeros too and then 5 random numbers coming from rnorm(1,0,1) and then
> > the rest of elements of the third column will be zeros.
> >
> > The first half of the fifth column of the matrix will be zeors.The
> > first FIFTEEN elements of the second half of the fourth column will be
> > zeros too and then 5 random numbers coming from rnorm(1,0,1).
> >
> > I tried to create 10 different functions ( one for 10, 20, 30, 40,
> > .... , 100 variables) but it's not efficient.
> >
> > Any help or advice for creating one function that can do all 10 kind
> > of variable cases would be appreciated.
> >
> >
> > Taka
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help