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Student Support Forum: 'Do I Dot product?' topicStudent Support Forum > General > "Do I Dot product?"

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09/19/06 06:00am

Look at the Dimensions of you matrix and recall how matrix dimensions are refered to in general mathematics, i.e. n X m. From what you write, I am guessing that you have a flat list such as
{1,2,3}

In[]:= Dimensions[{1,2,3}]
Out[]= {3}

Now consider:

In[]:= a = {{1, 2, 3}}
Out[]= {{1, 2, 3}}


In[]:= Dimensions[a]
Out[]= {1,3}

In[] := aT = Transpose[a]
Out[]= {{1}, {2}, {3}}


In[]:= Dimensions[aT]
Out[]= {3,1}

These dimensions match the standard requirement for dot products:

Look at the "shape":

In[]:= MatrixForm[a]

Out[]//MatrixForm=
1 2 3


In[]:= MatrixForm[aT]

Out[]//MatrixForm=
1

2

3

Now the Dot product:

In[]:= a . aT

Out[]= {{14}}


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Subject (listing for 'Do I Dot product?')
Author Date Posted
Do I Dot product? Prashanth 09/17/06 4:47pm
Correcting my question Prashanth 09/18/06 10:17pm
Re: Do I Dot product? Bob 09/19/06 02:32am
Re: Do I Dot product? Forum Modera... 09/19/06 06:00am
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