MATLAB: Creating a repeated matrix 2

matrix manipulation

Hi all,

I have

k1x=repmat(h(19,1), [3,1])   ;
k2x=repmat(h(37,1), [3,1])   ;
 k3x=repmat(h(55,1), [3,1])   ;
 k4x=repmat(h(73,1), [3,1])   ;
k5x=repmat(h(91,1), [3,1])   ;
kxtotal= [k1x; k2x;k3x;k4x;k5x];

h is a column of numnbers As you can see

               37=19+18
               55=37+18
               73=55+18.

So I add the number 18 to obtain the sequence 19, 37, 55, 73 …

Is there a better or clever way to construct kxtotal.

To be honest Isakson, I would prefer (as you did in my previous question) something like

   ixs    = repmat( [1:6], [3,1] );
   ktotal = arrayfun( @(ii) sprintf('S%u',ii), ixs(:), 'uni', false );

that is, the approach without the loop.

thanks

Best Answer

Try this

    ktotal = repmat( transpose( h([19:18:19+4*18]) ), [3,1] );
    ktotal = ktotal(:);

I use "transpose" instead of the blip, "'", because the latter is too easy to miss.

Related Solutions

MATLAB: Distribution of consecutive numbers

I don't think there's a way t do that without a loop (either explicit or with arrayfun).

%build list of patterns to search:
[n1, n2] = ndgrid(1:9);
patterns = [n1(:), n2(:)];
%search for each pattern with a loop:
x1 = reshape(x1, 1, []);  %need a row vector
count = zeros(size(patterns, 1), 1);
for row = 1:size(patterns, 1)
   count(row) = numel(strfind(x1, patterns(row, :)));  %despite its name strfind can be used to find patterns of numbers
end
%pretty display

table(patterns, count)

edit: actually I was completely wrong, it can easily be done without a loop, but temporarily requires much more memory:

[n1, n2] = ndgrid(1:9);
patterns = [n1(:), n2(:)];  
%count of pattern
transitions = permute([x1(1:end-1), x1(2:end)], [3 2 1]);
count = sum(all(patterns == transitions, 2), 3)
%pretty display
table(patterns, count)

edit again: Another option is to build the graph of the transitions and use the edgecount function:

g = graph(x1(1:end-1), x1(2:end));
[n1, n2] = ndgrid(1:9);
count = edgecount(g, n1(:), n2(:));
patterns = [n1(:), n2(:)];  
table(patterns, count)

MATLAB: Creating a repeated matrix

This is a more "clever" way:

   ixs    = repmat( [1:6], [3,1] );
   ktotal = arrayfun( @(ii) sprintf('S%u',ii), ixs(:), 'uni', false );

However, a for-loop is probably the "best" way:

    ktotal = cell( 6*3, 1 );
    for ii = 1:6
        ix = 3*(ii-1)+1;
        ktotal( ix : ix+2 ) = {sprintf('S%u',ii)};
    end

Best Answer

Related Solutions

MATLAB: Distribution of consecutive numbers

MATLAB: Creating a repeated matrix

Related Question