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Re: Symplify Table
*To*: mathgroup at smc.vnet.net
*Subject*: [mg109027] Re: Symplify Table
*From*: Bill Rowe <readnews at sbcglobal.net>
*Date*: Sun, 11 Apr 2010 04:29:58 -0400 (EDT)
On 4/10/10 at 6:52 AM, ertlejack at sbcglobal.net (John Ertle Jr.)
wrote:
>I want to subtract array A by 1/2 array B and put it in array C. I
>need something like this except more complicated later. This is
>what I have thus far:
>C:=C=Simplify[Table[A[i]-1/2*B[i],{i,1,9}]]
The first thing to note is in Mathematica the syntax A[i] does
not refer to the element i of array A. It is a function named A
evaluated at i, much different than an array even though this
notation can sometimes be usefully treated as being element i of
array A.
So, I will first create two arrays
In[3]:= a = RandomInteger[100, {3, 3}];
b = RandomInteger[10, {3, 3}];
then the third array c is computed simply as:
In[5]:= c = a - 1/2 b
Out[5]= {{99/2, 11/2, -2}, {121/2, 65, 78}, {84, 9/2, 60}}
No need to use Table or Simplify. And note:
In[6]:= ArrayQ[a]
Out[6]= True
But assigning values to d as if it were a 2D array by
In[7]:= Table[d[i, j] = RandomInteger[100], {i, 3}, {j, 3}];
ArrayQ[d]
gives
Out[8]= False
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