Quickly create a vector of ones and zeros

My question is if there is a way to create a vector of zeros

vec = 
    0 0 0 0 0 0 0 0

and specify a position lets say from the second until the fourth element to be ones.

vec = 
    0 1 1 1 0 0 0 0

Is there a quick way of doing this in Matlab avoiding loops?

Answer 1

[Youssef Khmou]

vectorization is possible :

 N=10;
 vec=zeros(N,1);
 positions=[2:4];
 vec(positions)=1;

[Stephen23]

Note that the square brackets are superfluous, and likely slow down the code:

https://www.mathworks.com/matlabcentral/answers/35676-why-not-use-square-brackets

[Innocent Okoloko]

For this short code the bracket is not superfluous. x=zeros(1,21) gives you a 1 by 21 matrix, which you may need to carefully index if you want to use x in oher calculations. Here the square brackets just give you a single vector x. You can indeed see that its about the shortest code for the task.

[Jos (10584)]

positions = 2:4;

would do, so the square brackets ARE superfluous ...

[Innocent Okoloko]

You are right. Indeed x=zeros(1,21) will give the same result, makingthe code even shorter and more efficient. I had previously encountered a situation that made me adopt the sqaure brackets and I tried to ransack through my codes, not enough time to do all that now. I guess it is just useful for contantenation e.g.

num=ones(1,5);

num=[num zeros(1,10)]

Answer 2

[Matt J]

 N=10;
 positions=[2:4];

 vec=sparse(1,positions,1,1,N);

and then optionally, if you want the vector in full form,

 vec=full(vec),

Answer 3

[Innocent Okoloko]

Faster coding

x=[zeros(1,10)];

x(2:4)=1

[Stephen23]

Note that the square brackets are superfluous, and likely slow down the code:

https://www.mathworks.com/matlabcentral/answers/35676-why-not-use-square-brackets

[Jos (10584)]

x = zeros(1,10)

will give the same result as your code, so the square brackets ARE superfluous ...

Answer 4

[Jos (10584)]

N = 10    % final length of NewVec 
pos1 = 3  % start index of the 1's
n1 = 4    % number of 1's

% one-liner. NewVec should not exist yet
NewVec([N pos1:pos1+n1-1]) = [0 ones(1,n1)]

Answer 5

[Khayalvili Ramu]

close all
clc
 
K=[1 2 3 6];
P=[1 2 2 2];
 
S=zeros(1,8);
T=zeros(1,length(S));
 
for i=0:(length(S)-1)
    S(1,i+1)=i;
    for k=0:length(K)-1
        T(1,k+1)=K(1,k+1);
        for l=length(K):length(T)-1
            T(1,l+1)=T(1,l-3);
        end
    end
end
 
S_temp=zeros(length(S),length(S));
 
j=0;
for i=0:length(S)-1
j=j+S(1,i+1)+T(1,i+1);
j=mod(j,8);
S([i+1 j+1])=S([j+1 i+1]);
S_temp(i+1,:)=S;
end
 
KS=zeros(1,length(P));
j=0;
for i=0:length(P)-1
    i_temp=mod(i+1,8);
    j=mod(j+S(1,i_temp+1),8);
    S([i_temp+1 j+1])=S([j+1 i_temp+1]);
    t=mod(S(1,i_temp+1)+S(1,j+1),8);
    ks=S(1,t+1);
    KS(:,i_temp)=ks;
    C=bitxor(KS,P);
end