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Thread Subject:
dot/inner product of vectors

Subject: dot/inner product of vectors

From: Snow White

Date: 29 Apr, 2010 10:22:04

Message: 1 of 6

Hello,

I have two vectors v1 and v2 and i want to take their dot product(inner product) as i want to eliminate calculation of an angle but the problem is that the vectors are not of equal length. v1 is 1x19 and v2 is 1x3. Is there a way to modify these and get a dot product?

Bye

Subject: dot/inner product of vectors

From: Torsten Hennig

Date: 29 Apr, 2010 10:43:06

Message: 2 of 6

> Hello,
>
> I have two vectors v1 and v2 and i want to take their
> dot product(inner product) as i want to eliminate
> calculation of an angle but the problem is that the
> vectors are not of equal length. v1 is 1x19 and v2 is
> 1x3. Is there a way to modify these and get a dot
> product?
>
> Bye

If you are only interested in the angle betweeen
the second vector and the first vector projected
from IR^19 to IR^3, you can calculate
v1(1)*v2(1)+v1(2)*v2(2)+v1(3)*v2(3)
as their inner product.
In general, an angle between vectors of different
dimensions is ambiguous and thus not well-defined.

Best wishes
Torsten.

Subject: dot/inner product of vectors

From: Snow White

Date: 29 Apr, 2010 11:05:05

Message: 3 of 6

I cant do that actually v1 is a vector of angle and v2 is another vector that has to be multiplied with the angles

Torsten Hennig <Torsten.Hennig@umsicht.fhg.de> wrote in message <741854198.42087.1272537831432.JavaMail.root@gallium.mathforum.org>...
> > Hello,
> >
> > I have two vectors v1 and v2 and i want to take their
> > dot product(inner product) as i want to eliminate
> > calculation of an angle but the problem is that the
> > vectors are not of equal length. v1 is 1x19 and v2 is
> > 1x3. Is there a way to modify these and get a dot
> > product?
> >
> > Bye
>
> If you are only interested in the angle betweeen
> the second vector and the first vector projected
> from IR^19 to IR^3, you can calculate
> v1(1)*v2(1)+v1(2)*v2(2)+v1(3)*v2(3)
> as their inner product.
> In general, an angle between vectors of different
> dimensions is ambiguous and thus not well-defined.
>
> Best wishes
> Torsten.

Subject: dot/inner product of vectors

From: John D'Errico

Date: 29 Apr, 2010 11:34:04

Message: 4 of 6

"Snow White" <gulesaman@gmail.com> wrote in message <hrbmkc$qor$1@fred.mathworks.com>...
> Hello,
>
> I have two vectors v1 and v2 and i want to take their dot product(inner product) as i want to eliminate calculation of an angle but the problem is that the vectors are not of equal length. v1 is 1x19 and v2 is 1x3. Is there a way to modify these and get a dot product?
>

You are not listening. What you have asked to do is
mathematically nonsensical.

A dot product is a well defined thing, but not between
things of different dimensions. So please explain what
these vectors represent, and what the angle is that you
wish to compute in that context, and we may be able
to help you.

John

Subject: dot/inner product of vectors

From: Snow White

Date: 29 Apr, 2010 13:18:04

Message: 5 of 6

Exactly! i knw a dot product is between vectors of the same length. i wanted to know is there a possibility of rearranging them such that this might be possible?

"John D'Errico" <woodchips@rochester.rr.com> wrote in message <hrbqrb$5s$1@fred.mathworks.com>...
> "Snow White" <gulesaman@gmail.com> wrote in message <hrbmkc$qor$1@fred.mathworks.com>...
> > Hello,
> >
> > I have two vectors v1 and v2 and i want to take their dot product(inner product) as i want to eliminate calculation of an angle but the problem is that the vectors are not of equal length. v1 is 1x19 and v2 is 1x3. Is there a way to modify these and get a dot product?
> >
>
> You are not listening. What you have asked to do is
> mathematically nonsensical.
>
> A dot product is a well defined thing, but not between
> things of different dimensions. So please explain what
> these vectors represent, and what the angle is that you
> wish to compute in that context, and we may be able
> to help you.
>
> John

Subject: dot/inner product of vectors

From: Mark Shore

Date: 30 Apr, 2010 03:08:04

Message: 6 of 6

"Snow White" <gulesaman@gmail.com> wrote in message <hrc0uc$9s9$1@fred.mathworks.com>...
> Exactly! i knw a dot product is between vectors of the same length. i wanted to know is there a possibility of rearranging them such that this might be possible?
>

How? Let's say you had a 3x1 and a 6x1 vector. Which one of the 20 (unscrambled) permutations would be the correct one?

Some questions answer themselves upon a little reflection.

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