Order a matrix by multiple column in r

Question

I have a matrix

df<-matrix(data=c(3,7,5,0,1,0,0,0,0,8,0,9), ncol=2)
rownames(df)<-c(\"a\",\"b\",\"c\",\"d\",\"e\",\"f\")

[,1] [,2]
a    3    0
b    7          


        

Answer 1

order function will help you out, try this:

df[order(-df[,1],-df[,2]),] 
  [,1] [,2]
b    7    0
c    5    0
a    3    0
e    1    0
f    0    9
d    0    8

The minus before df indicates that the order is decreasing. You will get the same result setting decreasing=TRUE.

df[order(df[,1],df[,2],decreasing=TRUE),]