Hi,
 
I have a matrix.
>a<-cbind(c("a","b","a"),c(4,3,6))
     [,1] [,2]
[1,] "a"  "4" 
[2,] "b"  "3" 
[3,] "a"  "6" 

I want to remove rows in matrix a whose first column has frequency less than 2.
in about example matrix a becomes
     [,1] [,2]
[1,] "a"  "4" 
[2,] "a"  "6" 




      
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