How to change if else to switch case in matlab

I have below code

clc
clear all
close all
s=[1 3 4 9 12 16 18 19 20 21];
for k=s   
    if k>2 & k<10
        a(k)=0;

    else if k>10 & k<20
          a(k)=1; 
        else a(k)=2;
        end
    end
end

I want to override it to switch case.how can I? please help me