how to find the nearest value?

hello guys

suppose i have a vector[s]

A=[ 1 2 3 4 5 6]
B=[6.1   5.1   4.1   3.1   2.1   1.1]

and

position_A=[10 20 30 40 50 60]

i want to find the nearest value of B in A

i have tried to do the following

for i=1: length(A)
    B(i)=min(abs(A-B(i)));
end

% now my vector B is [6 5 4 3 2 1]

i want to creat a vector that indicate the position of B, for example, the number 2 is the second element in A have position " position _A(2)=20",

i want to creat a vector "position_B" in a way that the number 2 in vector B have a position_B=20

thank you in advance

Answer 1

[Bruno Luong]

A=[ 1 2 3 4 5 6]

A = 1×6

1 2 3 4 5 6

B=[6.1   5.1   4.1   3.1   2.1   1.1]

B = 1×6

6.1000 5.1000 4.1000 3.1000 2.1000 1.1000

position_A=[10 20 30 40 50 60]

position_A = 1×6

10 20 30 40 50 60

loc = interp1(A,1:length(A),B,'nearest','extrap');
position_B = position_A(loc)

position_B = 1×6

60 50 40 30 20 10

B = A(loc)

B = 1×6

6 5 4 3 2 1

Answer 2

[dpb]

The builtin way in MATLAB is interp1

>> A=[1:6];
>> B=flip(A)+0.1;
>> posn=[10:10:60];
>> C=posn(interp1(B,A,A,'nearest','extrap'))
C =
  60   50    40    30    20    10
>>