An easier functional way to divide each Column of matrix by a row vector, element-wise?
- To: mathgroup at smc.vnet.net
- Subject: [mg127069] An easier functional way to divide each Column of matrix by a row vector, element-wise?
- From: "Nasser M. Abbasi" <nma at 12000.org>
- Date: Thu, 28 Jun 2012 04:01:40 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
I have a list like this 'mat' and 'v' like this
mat = { {a1,a2},{b1,b2} }
v = {v1,v2}
I want to generate
mat={ {a1/v1, a2/v2}, { b1/v1, b2/v2 } }
I can't just do mat/v since this does
mat={ {a1/v1, a2/v1}, { b1/v2, b2/v2 } }
I solved this 2 ways, but I am still not happy.
I think there should be an easier way.
method 1 (not too natural)
-------------------------------
Clear["Global`*"]
mat={{a1,a2},{b1,b2}};
v={v1,v2};
Transpose[Transpose[mat]/v]
Out[93]= { {a1/v1, a2/v2}, {b1/v1, b2/v2} }
method 2 (too complicated)
---------------------------
In[94]:= MapIndexed[Divide[#1,v[[#2[[2]]]]]&,mat,{2}]
Out[94]= { {a1/v1, a2/v2}, {b1/v1, b2/v2}}
method 3 (using a Table, oh no !)
------------------------------------
In[96]:= Table[mat[[i,j]]/v[[j]],{i,2},{j,2}]
Out[96]= {{a1/v1, a2/v2} , {b1/v1, b2/v2} }
method 4 (a not good way to do it )
----------------------------------------
In[108]:= mat.v/.Plus->List/.Times->Divide
Out[108]= {{a1/v1, a2/v2}, {b1/v1, b2/v2}}
I looked at real Mathematical tricks using Inenr and Outer and
something like this, but I do see a way so far. (I also did not
have my morning coffee yet), so I wanted to ask if
someone can see one of those elegant super functional
correct ways to do this.
ps. fyi, in that other system (starts with O and ends with VE)
I can do this like this:
mat=[1 2;3 4]
v=[5 10]
bsxfun(@rdivide,mat,v)
0.20000 0.20000
0.60000 0.40000
thanks,
--Nasser