grouping the users thereby sharing the subcarriers

 Nuser=4;
 Nsubcarrier=10;
 G is a matrix of (users,subcarriers)%image attached below
 C is subcarrier allocation to users %image attached below

could anyone tell me how to group the users as a result sharing of subcarriers takes place.

[Jan]

I've formatted the question to improve the readability.

What do you want as result of the "grouping"?

[Prabha Kumaresan]

As a result of grouping the subcarriers can be shared among the users which results in the improvement of throughput performance.

[Walter Roberson]

That description of grouping tells us nothing about how it needs to be implemented.

Answer 1

[Walter Roberson]

which_user = randi(Nuser, 1, Nsubcarrier);
newC = 0 * C;
idx = ((1:Nsubcarrier)-1) * Nuser + which_user;
newC(idx) = C(idx);

[Prabha Kumaresan]

but i couldnt find the sharing of subcarriers in newC(idx)

[Walter Roberson]

which_user = randi(Nuser, 1, Nsubcarrier);
C = 0 * G;
idx = ((1:Nsubcarrier)-1) * Nuser + which_user;
C(idx) = G(idx);

... if the point was to create C from G.

[Prabha Kumaresan]

before grouping if C was

[ 1 0 2 0 0 0 0 0;0 0 0 3 4 0 0 0;0 5 0 0 0 0 0 6;0 0 0 0 0 7 8 0]

after grouping C should be

[1 0 2 3 4 0 0 0;1 0 2 3 4 0 0 0;0 5 0 0 0 0 7 8 6;0 5 0 0 0 0 7 8 6]

Which means C is a matrix of [4*8]

4 users sharing 2 different subcarriers each.

[Prabha Kumaresan]

If G =

    0.0070    0.0103    0.0066    0.0033    0.0041    0.0027    0.0004    0.0050    0.0040    0.0046;
    0.0020    0.0016    0.0001    0.0018    0.0019    0.0008    0.0024    0.0036    0.0047    0.0044;
    0.0015    0.0011    0.0009    0.0011    0.0011    0.0022    0.0019    0.0018    0.0013    0.0028;
    0.0061    0.0033    0.0022    0.0037    0.0038    0.0011    0.0017    0.0029    0.0029    0.0019;

and C=

         0         0    0.0066         0         0         0         0         0         0         0;
    0.0020    0.0016         0    0.0018         0         0         0         0         0         0;
         0         0         0         0         0         0    0.0019         0         0         0;
         0         0         0         0    0.0038    0.0011         0    0.0029    0.0029    0.0019;

Now I want to group the users with respect to subcarriers. Suppose if I group user 1 with user 2 and user 3 with user 4 the corresponding subcarrier need to get shared which results in D=

 0.0020    0.0016    0.0066    0.0018         0         0         0         0         0         0;
    0.0020    0.0016    0.0066    0.0018         0         0         0         0         0         0;
         0         0         0         0    0.0038    0.0011    0.0019    0.0029    0.0029    0.0019;
         0         0         0         0    0.0038    0.0011    0.0019    0.0029    0.0029    0.0019;