Save values in a loop in a vector

Hi !

I would need some help for my home assignment cause im stucked. I need to iterate thru a vector and look for some values that are equal to 1.00, 0.80, 0.60, 0.40, 0.20 and 0.10. Then i need to store those values in another vector, how do i do this? Below u see the code for plotting those but i need to save them all in a vector so that i can make a nice table!

for i=1:size(d)

    if d(i)==1.00000
        disp(h(i))

    elseif d(i)==0.80000
        disp(h(i))

    elseif d(i)==0.60000
        disp(h(i))

    elseif d(i)==0.40000
        disp(h(i))

    elseif d(i)==0.20000
        disp(h(i))

    elseif d(i)==0.10000
        disp(h(i))

    end
end

Answer 1

[mbonus]

before the loop

v = zeros(size(d));

then just insert this line for each part of the if structure

v(i) = d(i);

If you need to get rid of the indexes with no values you can do this after the loop

v(find(0)) = [];

[mbonus]

a faster way to code though would be to recreate the loop and write it once rather than in the if structure if all of d meets the criteria.

[Daniel]

Thank you! The problem is that i got a error saying:

Error using zeros Requested 25001x25001 (4.7GB) array exceeds maximum array size preference. Creation of arrays greater than this limit may take a long time and cause MATLAB to become unresponsive. See array size limit or preference panel for more information.

[mbonus]

What is the size of d? I may have messed up with the zeros(), try

zeros(size(d))

[Daniel]

its an 25001x1 vector =)

[mbonus]

I messed up with zeros(). does the corrected version work?

[Daniel]

Hi again!

This wasnt what i wanted. I just need to know the i`s so that i can find the corresponding value in another vector. So, the vector d contains different denstity values corresponding to different altitudes. So, im saying that, find the i`s for different values for p and then use the i`s to find the corresponding values in z :)

[Daniel]

So, now i have this:

H = []; Z = [];

for i=1:size(d)

    if d(i)==1.00000
        Z(i) = z(i);
        H(i) = h(i);
    elseif d(i)==0.80000
       Z(i) = z(i);
        H(i) = h(i);

    elseif d(i)==0.60000
       Z(i) = z(i);
        H(i) = h(i);

    elseif d(i)==0.40000
        Z(i) = z(i);
       H(i) = h(i);

    elseif d(i)==0.20000
        Z(i) = z(i);
        H(i) = h(i);

    elseif d(i)==0.10000
        Z(i) = z(i);
        H(i) = h(i);

    end

end

H=find(H); Z=find(Z);

[Daniel]

and result i get is all i positions in vector d which is == to 1.00, 0.80 and so on. But what i need is to use those i`s and save the values in z(i) in a new vector Z

[mbonus]

Could post an example of what you get and what it should look like?

Answer 2

[Thorsten]

I found it a bit hard to understand what your are looking for. As far as I understood, this can solve your problem:

p =  [1.00, 0.80, 0.60, 0.40, 0.20, 0.10];

for i = 1:numel(p) % for all values in p
  Z{i} = z(h == p(i)); % find all positions in h that equal p(i), and assign the corresponding positions in z to a new variable Z
end

[Daniel]

For exampel: I have d=[1 22 31 41 51 6 7 8 9 10]; z=[1 2 3 4 5 6 7 8 9 10];

Now, i want to search in d for a value of 41. Then, give me that position, which in this case is on fourth column, hence i = 4

Now, go into the z vector and find me the value of column 4 and take that value and place it into Z vector :)

[Thorsten]

Z = z(d==41)

In my code above d == h and p(i) == 41. Because there can be, depending on your data, in principle one, two, or even more matches for d== 41, you have to store one, or two, etc values in Z, i.e., a different number of values for each i. That's why I use Z{i}. If you can guarantee that there is always one and only one match for each i, you can use Z(i).