Tim,
PS perhaps you should ask George Sheldrick whether he has ever found
himself constrained as to the algorithms he is able to program by the
semantics of Fortran.
I suspect his answer will be the same as mine!
Cheers
-- Ian
On Sat, Oct 16, 2010 at 8:50 AM, Tim Gruene wrote:
> Dear Ian,
>
>
On Oct 16, 2010, at 3:32 PM, Ian Tickle wrote:
> Hi Tim
>
> As I indicated previously, the Fortran code was only meant to define
> my statement of the problem so that there can be absolutely no
> ambiguity as to the question: the answer to the problem (if it exists)
> has nothing whatsoever to do
On Oct 16, 2010, at 12:32 PM, Ian Tickle wrote:
I have not yet come across a purely algebraic problem which possesses
semantics that couldn't be expressed in Fortran. That doesn't mean
there aren't any,
If it can't be expressed in FORTRAN, it probably can't be solved in
any other language e
Hi Tim
As I indicated previously, the Fortran code was only meant to define
my statement of the problem so that there can be absolutely no
ambiguity as to the question: the answer to the problem (if it exists)
has nothing whatsoever to do with the programming language used and I
don't see how it c
Dear Ian,
maybe you should switch from Fortran to C++. Then you would not be forced to
make nature follow the semantics of your programming language but can adjust
your code to the problem you are tackling.
The question you post would nicely fit into a first year's course on C++ (and of
course can
On Fri, Oct 15, 2010 at 8:11 PM, Douglas Theobald
wrote:
> Vectors are not only three-dimensional, nor only Euclidean -- vectors can be
> defined for any number of arbitrary dimensions. Your initial comment
> referred to complex numbers, for instance, which are 2D vectors (not 1-D).
> Obvious
Vectors are not only three-dimensional, nor only Euclidean -- vectors can be
defined for any number of arbitrary dimensions. Your initial comment referred
to complex numbers, for instance, which are 2D vectors (not 1-D). Obviously
scalars are not 3-vectors, they are 1-vectors. And contrary to
Any vector, whether in the 'mathematical' or 'physical' sense as
defined in Wikipedia, and which is defined on a 3D vector space
(Euclidean or otherwise - which I hope is what were talking about),
has by definition 3 elements (real or complex). This clearly excludes
all scalars (real or complex) wh
I couldn't resist:
What do you get when you cross an elephant with an orange?
Elephant.orange.sin(theta)
Frances
=
Bernstein + Sons
* * Information Systems Consultants
5 Brewster Lane, B
On Oct 15, 2010, at 12:14 PM, William G. Scott wrote:
>> As usual, the Omniscient Wikipedia does a pretty good job of giving the
>> standard mathematical definition of a "vector":
>>
>> http://en.wikipedia.org/wiki/Vector_space#Definition
>>
>> If the thing fulfills the axioms, it's a vector.
Maybe this will shed insight into the problem:
What do you get when you cross a mosquito with a rock climber?
Nothing. You can't cross a vector and a scalar
Have a good weekend,
JPK
> As usual, the Omniscient Wikipedia does a pretty good job of giving the
> standard mathematical definition of a "vector":
>
> http://en.wikipedia.org/wiki/Vector_space#Definition
>
> If the thing fulfills the axioms, it's a vector. Complex numbers do, as well
> as scalars.
It is a bit mo
On Oct 15, 2010, at 11:37 AM, Ganesh Natrajan wrote:
> Douglas,
>
> The elements of a 'vector space' are not 'vectors' in the physical
> sense.
And there you make Ed's point -- some people are using the general vector
definition, others are using the more restricted Euclidean definition.
Th
Douglas,
The elements of a 'vector space' are not 'vectors' in the physical
sense.
The correct Wikipedia page is this one
http://en.wikipedia.org/wiki/Euclidean_vector
Ganesh
On Fri, 15 Oct 2010 11:20:04 -0400, Douglas Theobald
wrote:
> As usual, the Omniscient Wikipedia does a pretty goo
As usual, the Omniscient Wikipedia does a pretty good job of giving the
standard mathematical definition of a "vector":
http://en.wikipedia.org/wiki/Vector_space#Definition
If the thing fulfills the axioms, it's a vector. Complex numbers do, as well
as scalars.
On Oct 15, 2010, at 8:56 AM,
On 10/14/10 11:22, Ed Pozharski wrote:
Again, definitions are a matter of choice
There is no "correct" definition of anything.
Definitions are a matter of community choice, not personal choice; i.e.
a matter of convention. If you come across a short squat animal with
split hooves rooting
Dear Ed,
I think you was "too fast and easy" in your comment.
Tensors are entities that have special rules when changing the coordinate
system.
That's not the case for "any matrix".
Best regards,
Sacha
De : CCP4 bulletin board [ccp...@jiscmail.ac.uk] d
On Thu, 2010-10-14 at 09:11 -0700, James Holton wrote:
> I wonder if anyone on this
> thread can explain to me the difference between a matrix and a
> tensor?
Matrix is a 2nd order tensor. Tensors may have any number of
dimensions, including zero. Tensor is just a fancy name for a
multidimensi
As I sit here listening to the giant "whoosh" sound of all the world's
biologists unsubscribing from the CCP4BB, I wonder if anyone on this
thread can explain to me the difference between a matrix and a tensor?
Since when are there biologists on this bb?
JPK
p.s. Is "whooshing" biologist-spec
On Thursday, October 14, 2010 09:11:50 am James Holton wrote:
> As I sit here listening to the giant "whoosh" sound of all the world's
> biologists unsubscribing from the CCP4BB, I wonder if anyone on this
> thread can explain to me the difference between a matrix and a tensor?
In invoking the l
As I sit here listening to the giant "whoosh" sound of all the world's
biologists unsubscribing from the CCP4BB, I wonder if anyone on this
thread can explain to me the difference between a matrix and a tensor?
I ask because I think stress and strain are mechanisms of radiation
damage, but whe
Ed,
I think you're confusing 'electric current' with 'electric current
density'. The first is a scalar, the second a vector. The current I
is defined as the surface integral of the density vector J with
respect to the element of area dA:
I = integral over S (J.dA) (how I wish we could use pro
Ed,
The direction of current in an electrical circuit has nothing to do
with any coordinate system. It is defined by convention in electricity
as the direction opposite to that in which the electrons are moving. So
the current is indicated as being from + to - in a circuit. Of course,
you may chan
Again, definitions are a matter of choice. Under your strict version I
still may consider electric current as vector, if I introduce the
coordinate system in the circuit. When I transform the coordinate
system (from clockwise to counterclockwise), current changes direction
with it. By the way, c
Electrical current is a 4-vector, is it not?
> Correct! - and an alternating electric current is represented as a
> complex number (then it's conventional to use the symbol 'j' for
> sqrt(-1) to avoid confusion with 'i', the symbol for electric
> current!). Since as you say electric current is a
Correct! - and an alternating electric current is represented as a
complex number (then it's conventional to use the symbol 'j' for
sqrt(-1) to avoid confusion with 'i', the symbol for electric
current!). Since as you say electric current is a scalar not a
vector, then a complex number has to be a
> The definition game is on! :)
>
> Vectors are supposed to have direction and amplitude, unlike scalars.
I think that this is part of the problem here. Whilst vector quantities do
possess both size and direction, not everything that possesses size and
direction is necessarily a vector by definiti
The definition of a vector as being something that has 'magnitude' and
'direction' is actually incorrect. If that were to be the case, a
quantity like electric current would be a vector and not a scalar.
Electric current is a scalar.
A vector is something that transforms like the coordinate system
The definition game is on! :)
Vectors are supposed to have direction and amplitude, unlike scalars.
Curiously, one can take a position that real numbers are vectors too, if
you consider negative and positive numbers having opposite directions
(and thus subtraction is simply a case of addition of a
29 matches
Mail list logo
