Repeat values in a vector

Assume

a1=[1 5 8];
b1=[6 4 5];
a2=[1 2 3 4 5 6 7 8];

Now I want to create a matching vector with values repeated as follows:

b2=[6 6 6 6 4 4 4 5];

Thanks in advance!

[Kevin Chng]

Have you tried it?

[KSSV]

Whats the logic behind b2? If it is a mere repeating...read about repelem and repmat.

Answer 1

[Andrei Bobrov]

b2 = b1(cumsum(ismember(a2,a1)));

[Florian]

Many thanks Andrei, also for answering my other question!

Answer 2

[Bruno Luong]

Another method:

[~,loc] = histc(a2,a1);
b2 = b1(loc)

yet another one

b2 = b1(interp1(a1,1:length(a1),a2,'previous'))

[Florian]

Many thanks!