Services & ResourcesWolfram ForumsMathGroup Archive

[Date Index] [Thread Index] [Author Index]

Re: Multiplying a constant to a matrix column

• To: mathgroup at smc.vnet.net
• Subject: [mg16336] Re: [mg16251] Multiplying a constant to a matrix column
• From: Jurgen Tischer <jtischer at col2.telecom.com.co>
• Date: Sun, 7 Mar 1999 01:05:53 -0500
• Organization: Universidad del Valle
• References: <199903050541.AAA13659@smc.vnet.net.>
• Sender: owner-wri-mathgroup at wolfram.com

Hyo Ahn,
try this:

mul[m_,a_,n_]:=MapAt[a*#&,#,n]&/@m

Jurgen

Hyo Ahn wrote:
> 
> Hi,
> 
> I would like to multiply a constant number to a given column of an existing
> matrix in Mathematica and I am having a hard time.
> 
> First, I have a 1000 x 3 matrix A.  There is no command that allow me to
> multiply a constant number to a specific column, so I extract three columns
> separately using
> 
> A1 = A[Range[1,1000],Range[1,1]];
> A2 = A[Range[1,1000],Range[2,2]];
> A3 = A[Range[1,1000],Range[3,3]];
> 
> fpr the first column and so on.  Then I multiply a constant to a extracted
> column which is a vector now.   Finally, I tried
> 
> A4 = ColumnJoin[A1,A2,A3]
> 
> but I found out that ColumnJoin command does not worked the way I expected
> it to be.
> 
> Could anyone know a simple solution to this problem?
> 
> Thanks.
> 
> Hyo Ahn
> KAERI

• References:
  • Multiplying a constant to a matrix column
    • From: "Hyo Ahn" <heahn@nanum.kaeri.re.kr>