extract small vector from large vector

b=[1;2;3;4;5;6;7;8;9;10;11;12;13;14;15];

a=zeros(3,1);

c=([a;b]);

d=(c(1,1):c(6,1));

e=(c(4,1):c(9,1));

please suggest me the way how can i write the code for vector d and e.

i want d vector as; d= [0;0;0;1;2;3] and

vector e as ; e=[1;2;3;4;5;6]

Answer 1

[Voss]

b = [1;2;3;4;5;6;7;8;9;10;11;12;13;14;15];
a = zeros(3,1);
c = [a; b]

c = 18×1

0 0 0 1 2 3 4 5 6 7

d = c(1:6,1) % ",1" not necessary since c only has one column

d = 6×1

0 0 0 1 2 3

e = c(4:9) % ",1" omitted

e = 6×1

1 2 3 4 5 6

[Chaudhary P Patel]

Thanks Sir,

[Voss]

You're welcome!

[Chaudhary P Patel]

sir, just tell me is it correct? if wrong please correct me.

utdelt=([1;2;3;4;5;6;7;8;9;10;11;12;13;14;15]);

nodof=3;

for i=1

for n=1:1:5

if n==1

Utdelt=([zeros(nodof,1); (utdelt(1:nodof,i))]);

eval(['Utdelt',num2str(n),'=[zeros(nodof,1); (utdelt(1:nodof,i))]']);

else

Utdelt=utdelt([(1+(n-2)*nodof):(6+(n-2)*nodof),(i)]);

eval(['Utdelt',num2str(n),'=[utdelt([(1+(n-2)*nodof):(6+(n-2)*nodof,(i)])]']);

end

end

[Voss]

I can't say whether it's correct since I don't know what it's supposed to do, but I would make Utdelt a matrix:

utdelt=([1;2;3;4;5;6;7;8;9;10;11;12;13;14;15]);
nodof=3;

Utdelt = zeros(6,5);

for i=1
    for n=1:1:5
        if n==1
            Utdelt(:,n) = [zeros(nodof,1); utdelt(1:nodof,i)];
        else
            Utdelt(:,n) = utdelt( 1+(n-2)*nodof : 6+(n-2)*nodof , i );
        end 
    end
end

Utdelt

Utdelt = 6×5

0 1 4 7 10 0 2 5 8 11 0 3 6 9 12 1 4 7 10 13 2 5 8 11 14 3 6 9 12 15

[Chaudhary P Patel]

sir i want to extract Utdelt as a column vector of 6X1.

[Voss]

But you calculate Utdelt in a loop that iterates 5 times.

If you want each Utdelt as a 6x1 column vector then how you had it was basically fine. Here is your code again, except without the eval statements, without all the unnecessary parentheses, fixing the indentation, and adding a missing end at the end.

utdelt=([1;2;3;4;5;6;7;8;9;10;11;12;13;14;15]);
nodof=3;
for i=1
    for n=1:1:5
        if n==1
            Utdelt = [zeros(nodof,1); utdelt(1:nodof,i)];
        else
            Utdelt = utdelt( 1+(n-2)*nodof : 6+(n-2)*nodof , i );
        end
        Utdelt
        % presumably, you would do something with Utdelt at this point
    end
end

Utdelt = 6×1

0 0 0 1 2 3

Utdelt = 6×1

1 2 3 4 5 6

Utdelt = 6×1

4 5 6 7 8 9

Utdelt = 6×1

7 8 9 10 11 12

Utdelt = 6×1

10 11 12 13 14 15

[Chaudhary P Patel]

thank you sir, in this loop i am calculating the f_s but when i am seeing the result the output is comin wrong.

utdelt=([1;2;3;4;5;6;7;8;9;10;11;12;13;14;15]);

Ktts=rand(6,6);

nodof=3;

for i=1

for n=1:1:5

if n==1

Utdelt = [zeros(nodof,1); utdelt(1:nodof,i)];

else

Utdelt = utdelt( 1+(n-2)*nodof : 6+(n-2)*nodof , i );

end

Utdelt

% presumably, you would do something with Utdelt at this point

end

f_s=Ktts*Utdelt;

end

[Voss]

That uses the value of Utdelt that was calculated for n=5. Previously calculated Utdelt values, i.e., for n=1 through n=4, are not used. Maybe that's what's wrong.