Math Forum / Mathematics / Numerical Analysis / May 2007

I have a gride of NxM nodes that works as follows. Each iteration,
each node multiplies the four connecting nodes (left,right,up,down) to
determine its next value. Node values are +/-1 so the grid doesn't
overflow with large numbers. I add a 1-node buffer around the grid of

I am trying to find roots of two bessel cross products and
particularly 10th first roots:
Jn(X)Yn(lx)-Jn(lx)Yn(x)=0
Jn(X)Yn'(lx)-Jn'(lx)Yn(x)=0

I am working on solving the system Ax=b by Linear Least Squares where A is a m*n matrix with m>=n.
I was asked to demonstrate that the LU factorization leads to problems when applied to the following ill-conditionned matrix
A = [ 0.00001 0
0 1];

Hello;
At time t1: the location w(=x,y,z) and the velocity dw(=dx/dt, dy/dt,
dz/dt) are known.
I need to advance the solution over a small interval dt using the

Is it possible to find the eigenvectors of a matrix without first finding
the associated eigenvalues?  Are there any algorithms to do this?
Jeremy Watts

this might be a silly question for some of you but i want to know. I
am trying to solve a 2x2 nonlinear system. The professor told me to
check the sign of the eigenvalues because it has something to do with
the stability of the solution. Can anyone explain me the difference of

Hello, can any one advise if the following statement is true or false
please? Your justification will be greatly appreciated too.
If f: R->R is continuous at 0 with f(0) = 0 and g: R->R is bounded
then the product fg is continuous at 0.

Hello;
If the integrand is a smooth function with a known finite jump
discontinuity within the range of integration, is it really necessary
to split-up the range and integrate over the subranges ????

What's the fastest way to make a choice from a set of N possibilities,
each with given probability P(i), i=,..,N ?
The probabilities are different each time a choice must be made.  N is
either 6 or 24.

The equation is d(c)/d(t) = k . d2(c)/d(x2)
for c(x,t) the boundary conditions are:
c(0,0) = 3.5
c(L,0) = 0

  I am looking for a clear derivation of this problem or maybe some Matlab code
to help me understand it.  I understand their is a closed for solution for this
problem and have tried several algorithm from journals with no luck in getting
the results to sum to one or nearly one.

As such, I have been using the IMSL library for numerical computation,
the one supplied with microsoft powerfortran 4.0. However I shall have
to move over to linux, and wont have access to the same library. Could
anybody please tell me whether there exists any free version of such

Could anybody help me with the derivative of the trace of a tensor
product? Unfortunately I don't have access to a good book to look it
up at the moment.
The problem is

I read Crisfiled's book in the library of my university and find it is
a very good finite element reference. In his book, he said the cods
can be download at ftp://ftp.cc.ic.ac.uk/pub/depts/aero/nonlin2/.
However, I can't connect the FTP (may be due to my bad net).

I am attempting to decipher a code that is using a combination of numerical methods to calculate the integral of the planck function with respect to frequency. For the power series and exponential series methods of the integration they use a simplified, non-dimensionalized ...