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From: James Ellis on 20 Mar 2010 16:13
My question is why does matlab do this?

I =

1 1 1 1

>> v1=I(1,1):I(1,3)

v1 =

1

How would I get v1=1 1 1 in this case? Im new to matlab and learning all the ins and outs, ive made a script which accepts a vector input such as

a, b, c, d

and has to make an NxN matrix

a-b, -b, 0
-b, b-c, -c
0, -c, c-d

which ive done as follows:

I= input('Input spring constant values as a row vector:');
[m,n]=size(I);
N=n-1;
v1=I(1,1):I(1,N);
v2=I(1,2):I(1,N+1);
v3=I(1,2):I(1,N);
K=diag(v1)+diag(v2)-diag(v3,1)-diag(v3,-1);

The problem is if the input vector's elements are all equal matlab just makes it a number and K comes out in the wrong dimension (its used later in multiplication so it needs to be the right dimensions).

Any advice?
From: Walter Roberson on 20 Mar 2010 16:17
James Ellis wrote:
> My question is why does matlab do this?
>
> I =
>
> 1 1 1 1
>
>>> v1=I(1,1):I(1,3)
>
> v1 =
>
> 1
>
> How would I get v1=1 1 1 in this case?

v1 = I(1,1:3);
From: James Ellis on 20 Mar 2010 17:06
Walter Roberson <roberson(a)hushmail.com> wrote in message <ho3agt$jdp$1(a)canopus.cc.umanitoba.ca>...
> James Ellis wrote:
> > My question is why does matlab do this?
> >
> > I =
> >
> > 1 1 1 1
> >
> >>> v1=I(1,1):I(1,3)
> >
> > v1 =
> >
> > 1
> >
> > How would I get v1=1 1 1 in this case?
>
> v1 = I(1,1:3);

hah classic I knew it would be something obvious.
Thanks!
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