Write some basic matrices functions.

Linear Algebra and the C Language · Wikibooks

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    From Wikibooks, under CC BY-SA 4.0, as the source states it. This page at Wikibooks.


    The code for certain matrix functions

    Diagonal matrix

    Copy/Paste into the octave window 

    %% Diagonal matrix
%%
%% Clear all user-defined variables
clear
%% ----------------------- */
%% ----------------------- */
function M = diagD(M)

r = size (M, 1);

%% Diagonal matrix
  for i=1:r

    M(i,i) = round(10*randn());
  end

endfunction
%% ----------------------- */
%% ----------------------- */
%%
%% === main ===
%% Clear the terminal
clc

rc = 6;
A  = zeros(rc);

%% Display A
A = diagD(A)

%% Display A as an indexed color image
figure(1), clf
imagesc(A)
axis square,  title('A')

%% === return(0) ===

    Lower triangular matrix

    Copy/Paste into the octave window

    %% Lower triangular matrix
%%
%% Clear all user-defined variables
clear
%% ----------------------- */
%% ----------------------- */
function M = trigL(M)

[r,c] = size (M);

%% Lower triangular matrix
for i=1:r
    for j=1:c

        if((i>=j))

           M(i,j) = round(10*randn());
        endif
    end
end

endfunction
%% ----------------------- */
%% ----------------------- */
%%
%% === main ===
%% Clear the terminal
clc

r = 6;
c = 6;

A  = zeros(r,c);

%% Display A
A = trigL(A)

%% Display A as an indexed color image
figure(1), clf
imagesc(A)
axis square,  title('A')

%% === return(0) ===

    Upper triangular matrix

     Copy/Paste into the octave window

    %% Upper triangular matrix
%%
%% Clear all user-defined variables
clear
%% ----------------------- */
%% ----------------------- */
function M = trigU(M)

[r,c] = size (M);

%% Upper triangular matrix
for i=1:r
    for j=1:c

        if((i<=j))

           M(i,j) = round(10*randn());
        endif
    end
end

endfunction
%% ----------------------- */
%% ----------------------- */
%%
%% === main ===
%% Clear the terminal
clc

r = 6;
c = 6;

A  = zeros(r,c);

%% Display A
A = trigU(A)

%% Display A as an indexed color image
figure(1), clf
imagesc(A)
axis square,  title('A')

%% === return(0) ===

    Symmetric matrix

    Copy/Paste into the octave window 

    %% Symmetric matrix
%%
%% Clear all user-defined variables
clear
%% ----------------------- */
%% ----------------------- */
function M = symmetric(M)

[r,c] = size (M);

%% Symmetric matrix
for i=1:r
    for j=1:c

           x = round(10*randn());

           M(i,j) = x;
           M(j,i) = x;
    end
end

endfunction
%% ----------------------- */
%% ----------------------- */
%%
%% === main ===
%% Clear the terminal
clc

r = 6;
c = 6;

A  = zeros(r,c);

%% Display A
A = symmetric(A)

%% Display A as an indexed color image
figure(1), clf
imagesc(A)
axis square,  title('A')

%% === return(0) ===

    Skewsymmetric matrix

    Copy/Paste into the octave window 

    %% Skewsymmetric matrix
%%
%% Clear all user-defined variables
clear
%% ----------------------- */
%% ----------------------- */
function M = skewsymmetric(M)

[r,c] = size (M);

%% Skewsymmetric matrix
for i=1:r
    for j=1:c

          if (i==j)

               M(i,j) = 0;
           else
               x = round(10*randn());

               M(i,j) =  x;
               M(j,i) = -x;
           endif
    end
end

endfunction
%% ----------------------- */
%% ----------------------- */
%%
%% === main ===
%% Clear the terminal
clc

r = 6;
c = 6;

A  = zeros(r,c);

%% Display A
A = skewsymmetric(A)

%% Display A as an indexed color image
figure(1), clf
imagesc(A)
axis square,  title('A')

%% === return(0) ===