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Thread Subject:
could anyone help home with this?

Subject: could anyone help home with this?

From: chet

Date: 7 Jun, 2011 15:19:02

Message: 1 of 6

the problem is that ,
I have calculated reduced compliance matrix that is A(i,j) which has the correct value of the 3*3 matrix
and next step wast to calculate the a(i,j) matrix which is the inverse of A(i,j)and the inverse matrix i.e, a(i,j)
matrix does not give the right value...
is my coding is mistake for inverse of A(i,j)?
could anyone tell me wat is mistake ..I am not able to find it out ..
thnk you,


for i = 1:3
for j = 1:3



A(i,j)= Qbar1(i,j)*h +Qbar2(i,j)*h +Qbar3(i,j)*h +Qbar4(i,j)*h ; % calc of A matrix

A_1(i,j) = Qbar1(i,j)*h ; %A matrix for 0 degree

A_2(i,j)= Qbar2(i,j)*h ; %A matrix for 45 degree

A_3(i,j)= Qbar3(i,j)*h; %A matrix for 90 degree

A_4(i,j)= Qbar4(i,j)*h ; %A matrix for -45 degree


a(i,j)=pinv(A(i,j));

a_1(i,j)=pinv(A_1(i,j)); % calc of a matrix the inverse of A matrix... %Warning: Matrix is singular to working precision.

a_2(i,j)=pinv(A_2(i,j));

a_3(i,j)=pinv(A_3(i,j));

a_4(i,j)=pinv(A_4(i,j));

end
end

Subject: could anyone help home with this?

From: Steven_Lord

Date: 7 Jun, 2011 15:35:51

Message: 2 of 6



"chet " <chetsunar@yahoo.com> wrote in message
news:islfh6$ei4$1@newscl01ah.mathworks.com...
> the problem is that , I have calculated reduced compliance matrix that is
> A(i,j) which has the correct value of the 3*3 matrix and next step wast to
> calculate the a(i,j) matrix which is the inverse of A(i,j)and the inverse
> matrix i.e, a(i,j)
> matrix does not give the right value... is my coding is mistake for
> inverse of A(i,j)?
> could anyone tell me wat is mistake ..I am not able to find it out .. thnk
> you,

Please do NOT both post to the newsgroup and email me directly; just post to
the newsgroup, as then others have a chance to respond (possibly before I
can) and I will also have an opportunity to respond if I am able.

Anyway, do NOT invert (or compute the pseudoinverse of) a matrix unless you
absolutely know your matrix is well conditioned and are required to do so.
If you're using your matrix to solve a system of equations, do NOT invert --
use backslash instead.

--
Steve Lord
slord@mathworks.com
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

Subject: could anyone help home with this?

From: Roger Stafford

Date: 7 Jun, 2011 21:15:07

Message: 3 of 6

"chet " <chetsunar@yahoo.com> wrote in message <islfh6$ei4$1@newscl01ah.mathworks.com>...
> ......
> a(i,j)=pinv(A(i,j));
> ......
- - - - - - - -
  Chet, as dpb has pointed out to you in thread 308864, the inverse of a matrix is very definitely not the same thing as the matrix of the inverses of its elements, and the same applies to the pinv's in this thread. In both 'inv' and 'pinv' all you get using scalars are their (conjugate) reciprocals.

Roger Stafford

Subject: could anyone help home with this?

From: chet

Date: 8 Jun, 2011 14:10:20

Message: 4 of 6

so how am i supposed to do Roger? as i'm new to matlab, so lots of problem... would be nice if u tell me straight way,

"Roger Stafford" wrote in message <ism4cr$j2k$1@newscl01ah.mathworks.com>...
> "chet " <chetsunar@yahoo.com> wrote in message <islfh6$ei4$1@newscl01ah.mathworks.com>...
> > ......
> > a(i,j)=pinv(A(i,j));
> > ......
> - - - - - - - -
> Chet, as dpb has pointed out to you in thread 308864, the inverse of a matrix is very definitely not the same thing as the matrix of the inverses of its elements, and the same applies to the pinv's in this thread. In both 'inv' and 'pinv' all you get using scalars are their (conjugate) reciprocals.
>
> Roger Stafford

Subject: could anyone help home with this?

From: Torsten

Date: 8 Jun, 2011 14:44:21

Message: 5 of 6

On 8 Jun., 16:10, "chet " <chetsu...@yahoo.com> wrote:
> so how am i supposed to do Roger? as i'm new to matlab, so lots of problem... would be nice if u tell me straight way,
>
>
>
> "Roger Stafford" wrote in message <ism4cr$j2...@newscl01ah.mathworks.com>...
> > "chet " <chetsu...@yahoo.com> wrote in message <islfh6$ei...@newscl01ah.mathworks.com>...
> > > ......
> > > a(i,j)=pinv(A(i,j));
> > > ......
> > - - - - - - - -
> >   Chet, as dpb has pointed out to you in thread 308864, the inverse of a matrix is very definitely not the same thing as the matrix of the inverses of its elements, and the same applies to the pinv's in this thread.  In both 'inv' and 'pinv' all you get using scalars are their (conjugate) reciprocals.
>
> > Roger Stafford- Zitierten Text ausblenden -
>
> - Zitierten Text anzeigen -


for i = 1:3
  for j = 1:3

    A(i,j)= Qbar1(i,j)*h +Qbar2(i,j)*h +Qbar3(i,j)*h +Qbar4(i,j)*h ; %
calc of A matrix
    A_1(i,j) = Qbar1(i,j)*h ; %A matrix for 0 degree
    A_2(i,j)= Qbar2(i,j)*h ; %A matrix for 45 degree
    A_3(i,j)= Qbar3(i,j)*h; %A matrix for 90 degree
    A_4(i,j)= Qbar4(i,j)*h ; %A matrix for -45 degree

  end
end

a=pinv(A);
a_1=pinv(A_1); % calc of a matrix the inverse of A matrix... %Warning:
Matrix is singular to working precision.
a_2=pinv(A_2);
a_3=pinv(A_3);
a_4=pinv(A_4);

Best wishes
Torsten.

Subject: could anyone help home with this?

From: chet

Date: 8 Jun, 2011 16:36:05

Message: 6 of 6

ok I got that the inverse does nt work here.........I need to take out the inverse of the matrix A to get the other matrix a. so how am i supposed to find the inverse if this syntax does not work?


Torsten <Torsten.Hennig@umsicht.fraunhofer.de> wrote in message <c3180e67-87ec-4657-a340-cdd387fa8d3a@v12g2000vby.googlegroups.com>...
> On 8 Jun., 16:10, "chet " <chetsu...@yahoo.com> wrote:
> > so how am i supposed to do Roger? as i'm new to matlab, so lots of problem... would be nice if u tell me straight way,
> >
> >
> >
> > "Roger Stafford" wrote in message <ism4cr$j2...@newscl01ah.mathworks.com>...
> > > "chet " <chetsu...@yahoo.com> wrote in message <islfh6$ei...@newscl01ah.mathworks.com>...
> > > > ......
> > > > a(i,j)=pinv(A(i,j));
> > > > ......
> > > - - - - - - - -
> > >   Chet, as dpb has pointed out to you in thread 308864, the inverse of a matrix is very definitely not the same thing as the matrix of the inverses of its elements, and the same applies to the pinv's in this thread.  In both 'inv' and 'pinv' all you get using scalars are their (conjugate) reciprocals.
> >
> > > Roger Stafford- Zitierten Text ausblenden -
> >
> > - Zitierten Text anzeigen -
>
>
> for i = 1:3
> for j = 1:3
>
> A(i,j)= Qbar1(i,j)*h +Qbar2(i,j)*h +Qbar3(i,j)*h +Qbar4(i,j)*h ; %
> calc of A matrix
> A_1(i,j) = Qbar1(i,j)*h ; %A matrix for 0 degree
> A_2(i,j)= Qbar2(i,j)*h ; %A matrix for 45 degree
> A_3(i,j)= Qbar3(i,j)*h; %A matrix for 90 degree
> A_4(i,j)= Qbar4(i,j)*h ; %A matrix for -45 degree
>
> end
> end
>
> a=pinv(A);
> a_1=pinv(A_1); % calc of a matrix the inverse of A matrix... %Warning:
> Matrix is singular to working precision.
> a_2=pinv(A_2);
> a_3=pinv(A_3);
> a_4=pinv(A_4);
>
> Best wishes
> Torsten.

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