Octave model matrix -

is there simple (non loop) way create model matrix in octave. in r use model.matrix() this.

i have array:

array = [1;2;3;2] 

and need (for regression reasons)

*(model = [1 0 0 0; 0 1 0 1; 0 0 1 0])* edit on side result model (colum 1 1, column 2 two's etc.: model = [1 0 0 ; 0 1 0 ; 0 0 1 ; 0 1 0] 

i can loop:

model = zeros(4,3);  i=1:4  model(i,array(i)) = 1;  end 

but nice in 1 step like:

model = model.matrix(array) 

i can include in formula straight away

you need turn values linear indices so:

octave:1> array = [1 2 3 2]; octave:2> model = zeros ([numel(array) max(array)]); octave:3> model(sub2ind (size (model), 1:numel(array), array)) = 1 model =     1   0   0    0   1   0    0   0   1    0   1   0 

because matrix sparse, possible optimization create sparse matrix instead.

octave:4> sp = sparse (1:numel(array), array, 1, numel (array), max (array)) sp =  compressed column sparse (rows = 4, cols = 3, nnz = 4 [33%])    (1, 1) ->  1   (2, 2) ->  1   (4, 2) ->  1   (3, 3) ->  1  octave:5> full (sp) ans =     1   0   0    0   1   0    0   0   1    0   1   0 

this take lot less memory many functions unable handle them , convert them full matrix anyway. whether worth dependent on want next.