how to select values of nx3 matrix where its index is equal to a value in other matrix

Hi, I have two arrays the first has nx3 dimension, and the second is mx1 dimension. i need to select the first array fileds where the index of it is equal to second array value. this is what is tried so far:

[ fid, fdim]=size(f);
[ fidnew, fdimnew]=size(fnew);
for j=1:1:fid
    if fid(j)==fnew(j)
        FF=f;
    end
end

then i have an error :

Index exceeds matrix dimensions.

Error in eee (line 26)
    if fid(j)==fnew(j)

how i can solve this?

[Stephen23]

What is i, and how is it defined?

[sana3 sal]

sorry it is "j" I will edit the text

Answer 1

[Preethi]

hi,

try this

i=1
for j=1:1:fid
    if j==fnew(j)
        FF(i)=f(j)
        i=i+1
    end
end

since fid is a scalar fid(j) is giving error..i tired with 4x3 and 5x1 matrices, it worked

Answer 2

[Stephen23]

"how to select values of nx3 matrix where its index is equal to a value in other matrix"

As far as I can tell, you can do that with basic indexing:

mat = f(fnew,:)