Exclusion of Columns in a matrix

My question is: I want to delete columns that possess the sum equal 1, however, when I use the function "for" occurs a problem....For each time that is deleted a column, the matrix is decreasing the number of columns, so that index used above exceed size of matrix....how can I solve this problem?

 for j=1:794;
    if S(j,1)==1;
        X(:,j)=[];
    end
end

when perform this command is showed:

 ???  Index of element to remove exceeds matrix dimensions.
thanks

Answer 1

[Andrei Bobrov]

X = X(:,~abs(sum(X) - 1)<1e3*eps);

OR

S = sum(X);
X = X(:,~abs(S - 1)<1e3*eps);

OR

X = X(:,abs(sum(X) - 1)>1e3*eps);

e.g.

>> X = randi(23,5)
X =
     7    12    18    23    20
    16    23     6    13     6
    16     8    12     4    19
     4    14    17     4     6
     3     6    21     6    22
>> X(:,3) = .2
X =
            7           12          0.2           23           20
           16           23          0.2           13            6
           16            8          0.2            4           19
            4           14          0.2            4            6
            3            6          0.2            6           22
>> X = X(:,abs(sum(X) - 1)>1e3*eps)
X =
     7    12    23    20
    16    23    13     6
    16     8     4    19
     4    14     4     6
     3     6     6    22
>>

[Alan]

Sorry, but I didn't understand....

This is all steps,

X(175X794);

for j=1:794;

S(j,1)=sum(X(:,j));

end

for j=1:794;

if S(j,1)==1;

X(:,j)=[];

end

end

Where can I use this in the command....sorry for my ignorance

[Andrei Bobrov]

in this is case not need use loops "for..end".

just use e.g.:

X = X(:,abs(sum(X) - 1)>1e3*eps);

[Andrei Bobrov]

see e.g.