Changing value when first time a value appears

A=[1; 1; 1; 1; 2; 2; 4; 4; 4; 4]

B=[4; 2; 7; 9; 5; 0; 2; 6; 1; 0]

I want to change the values of B to NaN whenever a value in A appears for the first time. i.e.

B=[NaN; 2; 7; 9; NaN; 0; NaN; 6; 1; 0]

Answer 1

[Walter Roberson]

A=[1; 1; 1; 1; 2; 2; 4; 4; 4; 4]

A = 10×1

1 1 1 1 2 2 4 4 4 4

B=[4; 2; 7; 9; 5; 0; 2; 6; 1; 0]

B = 10×1

4 2 7 9 5 0 2 6 1 0

[~, ia] = unique(A, 'stable')

ia = 3×1

1 5 7

B(ia) = nan

B = 10×1

NaN 2 7 9 NaN 0 NaN 6 1 0

[Mia Dier]

Thank you!!!