Galois field array generation...issues!

for the given code:

        primpoly = 1 0 1 1

        m = 4( assumed)
        indx = [0:1:2.^m-1]; %power index
        for r = 1:length(indx)
           U = gftuple(indx,primpoly,p)
        end

I want U to be listed out in a p.^m-1 by m+1 array and not separately. so that i can access each row of U for further computation. but with the above i get U separately for each loop run and the previous U is over-written.

Also, Can i code it without using gftuple, like without any built-in function?

Answer 1

[Walter Roberson]

U(r,:) = gftuple(indx,primpoly,p);

[Malik]

this generates only one U at the end several times. I want all possible U's generated by the loop to be saved up in ONE matrix/table. the o/p here is:

U =

     1     0     1
     1     0     1
     1     0     1
     1     0     1
     1     0     1
     1     0     1
     1     0     1
     1     0     1

several times! which is not the desired output.

[Walter Roberson]

U(r,:) = gftuple(indx(r),primpoly,p);

[Malik]

yes this gives the right output but several times if i do not put ';' this means U is being produced several times, cant it be reduced to just once....n Thanks!

[Walter Roberson]

Sorry, I do not have the Communications Toolbox to test with.

Are all of the output U's exactly the same? When there is an assignment to part of an array and you do not have a semi-colon, MATLAB outputs the entire array.

[Malik]

the output U is as follows:

U =

     1     0     0
     0     1     0
     0     0     1
     1     0     1
     1     1     1
     1     1     0
     0     1     1
     1     0     0

But my objective was to call this U once but here this U gets repeated 8 times (the exact same U, dont know why).

[Walter Roberson]

Is your code line literally

primpoly = 1 0 1 1

instead of

primpoly = [1 0 1 1]

??

[Walter Roberson]

I do not know why the output would be exactly the same each time when indx(r) is used, but I do see in the documentation that you do not need the loop.

U = gftuple( indx(:), primpoly, p )

Notice passing in a column of indices instead of the row you were using.

[Malik]

well U = gftuple( indx(:), primpoly, p ) actually works! Thanks! and yes it is supposed to be [1 0 1 1].

[Malik]

Is there some way to code this gf tuple function without using the built-in function?

[Walter Roberson]

Probably, but I have not researched to find out what the expected output would be.