How to bin IDX based on previous IDX value?

Hello,

I have an array:

a = [0 0 1 2 2 1 2 2 1 0 1 0 2];

I would like to bin the IDX of 2 into three different variables.

1) B = IDX of 2 if the preceding IDX == 1

2) C = IDX of 2 if the preceding IDX == 0

3) D = IDX of 2 if the preceding IDX == 2

Any suggestions?

Answer 1

[Walter Roberson]

a = [0 0 1 2 2 1 2 2 1 0 1 0 2];
temp = [-1 a];
idx2 =  temp(2:end) == 2;
b_loc = idx2 & temp(1:end-1) == 1;
c_loc = idx2 & temp(1:end-1) == 0;
d_loc = idx2 & temp(1:end-1) == 2;
new_a = string(a);
new_a(b_loc) = "B";
new_a(c_loc) = "C";
new_a(d_loc) = "D";

new_a

new_a = 1×13 string array
    "0"    "0"    "1"    "B"    "D"    "1"    "B"    "D"    "1"    "0"    "1"    "0"    "C"

[Dc215905]

Thank you!

Answer 2

[the cyclist]

Is this what you mean?

a = [0 0 1 2 2 1 2 2 1 0 1 0 2];

loc2 = a(2:end)==2;
pre  = a(1:end-1);

b = 1 + find(loc2 & (pre==1))

b = 1×2

4 7

c = 1 + find(loc2 & (pre==0))

c = 13

d = 1 + find(loc2 & (pre==2))

d = 1×2

5 8

[Dc215905]

Yup, that works too. Thanks!