Re: Help: Column/Row Vector

*To*: mathgroup at smc.vnet.net*Subject*: [mg4290] Re: Help: Column/Row Vector*From*: Harald Berndt <haraldb at nature.berkeley.edu>*Date*: Sat, 29 Jun 1996 03:55:22 -0400*Organization*: University of California Forest Products Lab*Sender*: owner-wri-mathgroup at wolfram.com

khinast at nld.chee.uh.edu wrote: > > Hi, > > I have two vectors x=(x1,x2) and y = (y1,y1). How can I persuade Mathematica > that e.g. x is a column vector and y is a row vector, which is kind of > important for their multiplication . No, not really. Not in Mathematica, anyway. You just need to make sure you use the right vector "product:" inner, outer, and (for lack of a better word) direct. The latter is just an element-by-element multiplication: In[35]:= {x1, x2} {y1, y2} Out[35]= {x1 y1, x2 y2} The inner product is the usual scalar product or dot product of the two vectors, regardless of order/orientation: In[36]:= {x1, x2}.{y1, y2} Out[36]= x1 y1 + x2 y2 In[37]:= {y1, y2}.{x1, x2} Out[37]= x1 y1 + x2 y2 The outer, or tensor, product is the dyad of the two vectors, and here, the order matters: In[38]:= Outer[ Times, {x1, x2}, {y1, y2} ] Out[38]= {{x1 y1, x1 y2}, {x2 y1, x2 y2}} In[39]:= Outer[ Times, {y1, y2}, {x1, x2} ] Out[39]= {{x1 y1, x2 y1}, {x1 y2, x2 y2}} > I've studied the help page for hours, with no result. So could > someone please help me. My email address is: > > khinast at nld.chee.uh.edu > > Joh. I hope that helps a bit. -- _______________________________________________________________ Harald Berndt University of California Research Specialist Forest Products Laboratory Phone: 510-215-4224 FAX:510-215-4299 _______________________________________________________________ ==== [MESSAGE SEPARATOR] ====