extract elements and build the remain vector

Hello Community,

i need your help.

A vector v has 128 elements with random numbers.

The elements of index 1 21 31 41 should be etracted, and saved as vector a.

the remain elements of vector v should be saved as vector b.

my version consist two for loops which is in deed a bad solution for large vectors.

PS: the vectors are not constant.

maybe someone could finish the algorithm:

v = 1:128;
a = v([1 21 31 41]);

Answer 1

[Image Analyst]

Use setdiff():

N = 1600;
v = 1:N;
a = [2 59 87 113]

extracted = v(a)
otherIndexes = setdiff(1:length(v), a);
b = v(otherIndexes)

[Marko]

Perfect!

A nice code snippet!

Answer 2

[David Hill]

a=v([1 21 31 41]);
b=v([2:20,22:30,32:40,42:end]);

[Marko]

Hello David,

thank you for your fast response. I'm sorry for beeing not specfic enough.

Could you develop a code snippet also for non-constant vectors v,a ?

Best,

MJ

[David Hill]

Depending on what random numbers you want, use rand() or randi() functions (assuming uniform distribution)

v=A*rand(1,128)-B;%generates random numbers between -B:A-B

[Marko]

ok, i see i was not clear enough.

i try beeing a precicsly as possible:

Vector v has N elements:

N = 1600;
v = 1:N;

Vector a is given and contains integer number: e.g.

a = [2 59 87 113]

How could an algorithm extract a from v and save the remaining elements in vector b.

Important: the vectors v and a have not a constant number of elments, they can change.

The solution should be for this example:

b=[1 3 ... 58 60 ... 86 88 ... 112 114 ... 1600]

[David Hill]

b=v(~ismember(v,a));

[Marko]

Perfect!

You are a genius!