find indexes of two values that between them there is specific number

i have vector A=[1 5 3 1 10 38 27] and value B=2 i want to find the nearest value to B by interpolate values that B is between them. like this: 2 is between 1,5 and 3,1 if 2 is closest to value from linear interpolation between 1,5 i want to chose this number if 2 is closest to value from linear interpolation between 3,1 i want to chose this number

thanks!

[David Hill]

How is 2 between 5, 3?

[Keren Grinberg]

Oops, my mistake I edited the question

Answer 1

[Davide Masiello]

clear,clc

A = [1 5 3 10 38 27];
B = 2;

% Interpolattion values
idx  = 1:2:2*length(A)-1;
newA = interp1(idx,A,1:idx(end))

newA = 1×11

1.0000 3.0000 5.0000 4.0000 3.0000 6.5000 10.0000 24.0000 38.0000 32.5000 27.0000

interpA = newA(2:2:end)

interpA = 1×5

3.0000 4.0000 6.5000 24.0000 32.5000

% Find closest interpolated value
[~,k] = min(abs(interpA-B));
disp(interpA(k))

     3

% Indexes of elements in A that enclose the closest interpolated value
A_idxs = [k,k+2]

A_idxs = 1×2

1 3

Answer 2

[David Hill]

A=[1 5 2.5 1 2.1 38 1.4 2.7 27 2.3 1.9 2.6 2.7 9 10 1.2];
B=2;
f=A-B;
F=find(f<0);
b=[];
for k=1:length(F)
    try 
        [~,i]=min([abs(f(F(k))),abs(f(F(k)-1))]);
        b=[b,A(F(k)-i+1)];
    end
    try
        [~,i]=min([abs(f(F(k)+1)),abs(f(F(k)))]);
        b=[b,A(F(k)-i+2)];
    end
end
%b array will be A-values closest to B (when adjacent values of A are
%between B)