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Multiply a constant to a matrix column

• To: mathgroup at smc.vnet.net
• Subject: [mg16266] Multiply a constant to a matrix column
• From: heahn at nanum.kaeri.re.kr (Hyo ahn)
• Date: Fri, 5 Mar 1999 00:41:27 -0500
• Organization: kaeri
• Sender: owner-wri-mathgroup at wolfram.com

Hi,

I would like to multiply a constant number to a certain 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 (let say I want to multiply
100 to the second 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]];

Then I multiply a constant to a extracted
column which is a vector now.   So I did

A2b = 100 A2;

Then I recombined the columns as

A4 = ColumnJoin[A1,A2b,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

• Follow-Ups:
  • Re: Multiply a constant to a matrix column
    • From: "Wolf, Hartmut" <hwolf@debis.com>