MaplePrimes - answers and comments on Question, Adding matrix diagonally

Own procedure.

Jarekkk — Tue, 07 Feb 2012 02:44:27 Z

I would create my own procedure for this. I don't know if there is anything "easier".

Edit: The procedure could look like this (I suppose that L is a list of 3x3 matrices):

diag_matrix := proc (L)
local M, i;
M := Vector(nops(L)):
M[1] := Matrix(2*nops(L)+1, L[1]);

for i from 2 to nops(L) do
M[i] := LinearAlgebra[DiagonalMatrix]([Matrix(2*i-2), L[i], Matrix(2*(nops(L)-i))])
end do;

return add(M[i], i = 1 .. nops(L));
end proc:

overlap

pagan — Tue, 07 Feb 2012 06:59:09 Z

restart:
randomize():
interface(rtablesize=100):

N:=3:
number:=4:

L:=[seq(LinearAlgebra:-RandomMatrix(N),i=1..number)];

       [[ 58  -42  -62]  [ 62  -47  -79]  [-78  -85  39]  [ -2  -97   92]]
       [[             ]  [             ]  [            ]  [             ]]
  L := [[ 25   23  -88], [ -8  -71   -6], [-38   -3  56], [-13  -31  -34]]
       [[             ]  [             ]  [            ]  [             ]]
       [[-49  -53  -30]  [-15   57   79]  [-73   58  52]  [-86  -37  -92]]

M:=Matrix((N-1)*number+1):

for i from 1 to number do
   sz := (N-1)*(i-1)+1;
   M[sz..sz+N-1,sz..sz+N-1]:=
   M[sz..sz+N-1,sz..sz+N-1]+L[i];
end do:

M;

                [ 58  -42  -62    0    0    0    0    0    0]
                [                                           ]
                [ 25   23  -88    0    0    0    0    0    0]
                [                                           ]
                [-49  -53   32  -47  -79    0    0    0    0]
                [                                           ]
                [  0    0   -8  -71   -6    0    0    0    0]
                [                                           ]
                [  0    0  -15   57    1  -85   39    0    0]
                [                                           ]
                [  0    0    0    0  -38   -3   56    0    0]
                [                                           ]
                [  0    0    0    0  -73   58   50  -97   92]
                [                                           ]
                [  0    0    0    0    0    0  -13  -31  -34]
                [                                           ]
                [  0    0    0    0    0    0  -86  -37  -92]

And as a procedure,

overlap:=proc(LL::list(Matrix(square)))
  local i, n, numb, m, rng, sz;
  n := op([1,1],LL[1]);
  numb := nops(LL);
  m:=Matrix((n-1)*numb+1):
  for i from 1 to numb do
    sz := (n-1)*(i-1)+1;
    rng := sz..sz+n-1;
    m[rng,rng] := m[rng,rng]+LL[i];
  end do:
  m;
end proc:

overlap(L);

                [ 58  -42  -62    0    0    0    0    0    0]
                [                                           ]
                [ 25   23  -88    0    0    0    0    0    0]
                [                                           ]
                [-49  -53   32  -47  -79    0    0    0    0]
                [                                           ]
                [  0    0   -8  -71   -6    0    0    0    0]
                [                                           ]
                [  0    0  -15   57    1  -85   39    0    0]
                [                                           ]
                [  0    0    0    0  -38   -3   56    0    0]
                [                                           ]
                [  0    0    0    0  -73   58   50  -97   92]
                [                                           ]
                [  0    0    0    0    0    0  -13  -31  -34]
                [                                           ]
                [  0    0    0    0    0    0  -86  -37  -92]

Hi, may I know why everytime I press enter,

serena88 — Sun, 12 Feb 2012 03:28:03 Z

Hi, may I know why everytime I press enter, the for loop gives me an increase in multiple of two? for example, first it gives me 58, then if i press enter gain, it gives me 116, and if i press enter again, it gives me 174 and so on...

Further on question

serena88 — Mon, 13 Feb 2012 22:15:25 Z

Hi, Thank you for your help.

I have now a further question. I only have one matrix : se00:=Matrix([[4,2,-1],[2,16,2],[-1,2,4]])

I want to add them up as above. Here is what I did :

>>num:=16

>>ie0:=Matrix(33)

>>for m from 1 to num-1 do

n1:=m*2+1:

ie0[n1..n1+2,n1..n1+2]:=se00

end do

Problem : it does not give me a 33x33 matrix

Please advice.

Thx

further example

pagan — Mon, 13 Feb 2012 22:31:48 Z

@serena88

restart:

se00:=Matrix([[4,2,-1],[2,16,2],[-1,2,4]]):

N:=LinearAlgebra:-RowDimension(se00);

number:=(33-1)/(N-1);

ie0:=Matrix(33):

for i from 1 to number do
   sz := (N-1)*(i-1)+1;
   ie0[sz..sz+N-1,sz..sz+N-1]:=ie0[sz..sz+N-1,sz..sz+N-1]+se00; # add corners
   ### ie0[sz..sz+N-1,sz..sz+N-1]:=se00; # overwrite corners
end do:

interface(rtablesize=33):

ie0;

How do i pick a value in the matrix?

serena88 — Wed, 15 Feb 2012 17:06:07 Z

Hi, may I know how do i pick a value in the matrix to do further calculation please? for example, the matrix above, i would like the pick up the value in row 3 column 3 which is 32. Please advice. thanks