Re: [femm] lua script data storage in vectors and matrices

[David Meeker <dmeeker@xxxxxxxx>]

ac090960 wrote:

> Hello guys,
> Inside a lua script I m not able to create/define a vector or matrix
> in which store data coming from femm calculation i.e. Bx By and so on.
> Are there any way or procedure to create vectors and matrices or
> equivalent other method to store data like B, H, J ... coming from 
> femm calculation using a lua command /language?
>
> Any help and suggestion is welcome
> Arnoldo
Check out section 11.3 in "Programming in Lua" at 
http://www.inf.puc-rio.br/~roberto/luabook1.pdf
Cribbing a bit from the book:

*
11.2 Matrices and multi-dimensional arrays

*There are two main ways to represent matrices in Lua. The first one is 
to use an array of arrays, that is, a table wherein each element is 
another table. For instance, you can create a matrix of zeros with 
dimensions N, M with the following code:

mt = {} -- create the matrix
for i=1,N do
mt[i] = {} -- create a new row
for j=1,M do
while j <= M do
mt[i][j] = 0
end
end

Because tables are objects in Lua, you have to explicitly create each 
row to create a matrix. At one hand, this is certainly more verbose than 
simply declaring a matrix, as you do in C or Pascal. On the other hand, 
that gives you more flexibility. For instance, you can create a diagonal 
matrix changing the line

for j=1,M do

in the previous example to

for j=i,M do

With that code, the diagonal matrix uses only half the memory of the 
original one.

The second way to represent a matrix in Lua is composing the two indices 
into a single one. If the two indices are integers, you can multiply the 
first one by a constant and then add with the second index. With this 
approach, our matrix of zeros with dimensions N, M would be created with

mt = {} -- create the matrix
for i=1,N do
for j=1,M do
mt[i*M+j] = 0
end
end



--
David Meeker
email: dmeeker@xxxxxxxx
www: http://femm.berlios.de/dmeeker