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Re: Binary Vector Manipulation
*To*: mathgroup at smc.vnet.net
*Subject*: [mg84103] Re: Binary Vector Manipulation
*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
*Date*: Mon, 10 Dec 2007 20:34:41 -0500 (EST)
*Organization*: The Open University, Milton Keynes, UK
*References*: <fjj183$frv$1@smc.vnet.net>
Tara.Ann.Lorenz at gmail.com wrote:
> I am need of assistance programming the following scenario:
>
> I have two vectors composed of 0's and 1's. Vector "A" has 5% 1's
> (and 95% 0's) while Vector "B" has 50% 1's and 50% 0's.
>
> First, I would like to change Vector B to have a "1" in every place
> that Vector A also has a "1" (in other words, I will then have more
> than 50% 1's in Vector B once this step is completed).
>
> Then, I would like to *randomly* return Vector B back to a 50/50
> distribution of 1's and 0's.
>
> I greatly appreciate any proposed programming methods.
The following function should do what you are asking for.
In[1]:= myFun[A : {0 | 1 __}, target : {0 | 1 __}] /;
Length@A <= Length@B && EvenQ[Length@B] :=
Module[{B, len, pos},
B = target;
len = Length@B;
B = ReplacePart[B, Position[A, 1] -> 1];
While[Count[B, 1] - len/2 > 0,
pos = RandomInteger[{1, len}];
If[B[[pos]] == 1, B[[pos]] = 0];
];
B
]
Then, we make up some data and check that myFun works correctly.
In[2]:= Needs["Combinatorica`"]
A = RandomPermutation[Join[Table[1, {5}], Table[0, {95}]]];
B = RandomPermutation[Join[Table[1, {50}], Table[0, {50}]]];
c = myFun[A, B];
c == B
Count[#, 1] & /@ {A, B, c}
Out[6]= False
Out[7]= {5, 50, 50}
Regards,
--
Jean-Marc
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