Re: Multiplying a constant to a matrix column
- To: mathgroup at smc.vnet.net
- Subject: [mg16394] Re: [mg16251] Multiplying a constant to a matrix column
- From: Mitch Stonehocker <derivado at campus.ccm.itesm.mx>
- Date: Thu, 11 Mar 1999 02:16:57 -0500
- References: <199903050541.AAA13659@smc.vnet.net.>
- Sender: owner-wri-mathgroup at wolfram.com
Hi, I hope this helps. First create a matrix A1=Table[{n,n+1,n+2},{n,1,5}] {{1,2,3},{2,3,4},{3,4,5},{4,5,6},{5,6,7}} Second Identify which column you wish to apply your rule ColChange=2; Third apply the rule (in this example 2*column) A2=Transpose[ A[1] /. Transpose[A1][[ColChange]] \[Rule] 2 * Transpose[A1][[ColChange]] {{1,2,3,4,5},{4,6,8,10,12},{3,4,5,6,7}} Now you back to (a new) A1 with the change (2*column) A1=Transpose[A2] {{1,4,3},{2,6,4},{3,8,5},{4,10,6},{5,12,7}} I hope that's the result your looking for. Regards, Mitch Stonehocker Mexico City 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>
- Multiplying a constant to a matrix column