MATLAB: How to make vector by value and index

mapping index and valuevector

Hello, I try to make vector by value and index.

Please see my code.

Tk=(rand(1,k)*N0); % Tk is index of h, k is index number, N0 is maxmum index. 
Tk=sort(Tk); 
Ck=randn(1,k); %Ck is value matched index of Tk.
h=zeros(1,N0); % h is vector with index of Tk and value of Ck.(the other index has all zero.)

Example)

Tk = 2.2, 5.4
Ck = 44, 67
h = 0 0 ...0 0 0 44 0 0 0 0 0 ...0 67 0 0 0 0...

Please explain me.

Best Answer

Tk = randperm(N0, k);     %k integers from 1 to N0, no need to sort them
Ck = randn(1,k);
h = zeros(1, N0);
h(Tk) = Ck;

This can be done in two lines as

h = zeros(1, N0);
h( randperm(N0, k) ) = randn(1, k);

I also recommend that for the future you read about randi()

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Please, use the {} Code button above the field you're writing your question to make the post be readable.

Also, you should learn about the array concept of Matlab. Your equations look kind of like scalar products, so most likely you can significantly shorten your code and avoid typos this way.

With respect to your question, in this case it's easier to loop with a counter from 1:7, create the respective ta from this and instead of writing data to scalars, save them in arrays. Such as

ta=zeros(1,7);
qe=zeros(1,7); 
for cnt=1:7
  ta(cnt)=cnt*5+15;
  qe(cnt)=...;
  ...
end
plot(ta,qe)

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 H = randn(M, N, k) + j*randn(M, N, k);   %no need for loop
 c = num2cell(H, [1 2]);                  %split H into cell array along 3rd dimension
 for u=1:k
     indices = [1:u-1 u+1:k];             %get numbers 1:k without u
     Hi(:, :, u) = vertcat(c{indices});   %use cell array to comma separated list expansion to feed vertcat
 end

Best Answer

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