R programming Missing value error

Question

I'm executing the following block of code:

m <- matrix(c(1:5,NA,7,7,NA),
nrow=3,ncol=3,byrow=T)
print(m)
for ( i in 1:dim(m)[[1]] ) {
mm <- sort(m[i,],na.last=c(NA,NA,T)[[i]])
for ( j in 1:(length(mm)-1) ) {
if ( mm[[j]]==mm[[j+1]] ) {
cat(i,j,mm[[j]],fill=T)
}
}
}

On running this code i get an error:

 "Error in if (mm[[j]] == mm[[j + 1]]) { : missing value where TRUE/FALSE needed "

Answer 1

You can achieve this by wrapping isTRUE() around your if-condition:

for ( i in 1:dim(m)[[1]] ) {
  mm <- sort(m[i,],na.last=c(NA,NA,T)[[i]])
  for ( j in 1:(length(mm)-1) ) {
    if ( isTRUE(mm[[j]]==mm[[j+1]]) ) {
      cat(i,j,mm[[j]],fill=T)
    }
  }
}

Output:

3 1 7