Data Mining - (Missing Value|Not Available) NA in R.
NA (Not Available|Missing Values) is a logical constant.
See
?NA
> str(NA)
logi NA
NA values have a class. There are integer NA, character NA, etc.
NA means “Not Available”.
NA is a logical constant of length 1 which contains a missing value indicator.
> is.na(NA)
[1] TRUE
> v = c(1, NA, 2)
> is.na(v)
[1] FALSE TRUE FALSE
> is.na(NaN)
[1] TRUE
vapply(data.frame, function(x) mean(!is.na(x)), numeric(1))
v = c(1, NA, 2)
> v[!is.na(v)]
[1] 1 2
colA = c(1, 2, 3, 4, NA, 6)
colB = c(1, 2, NA, 4, 5, 6)
m=cbind(colA,colB)
m
colA colB
[1,] 1 1
[2,] 2 2
[3,] 3 NA
[4,] 4 4
[5,] NA 5
[6,] 6 6
rowWithoutNa = complete.cases(m)
rowWithoutNa
[1] TRUE TRUE FALSE TRUE FALSE TRUE
m[rowWithoutNa,]
colA colB
[1,] 1 1
[2,] 2 2
[3,] 4 4
[4,] 6 6
to eliminate any row in the data frame that's got a missing value in it, there's a nice function called na.omit
myDataFrame=na.omit(myDataFrame)
in a variable
with(dataFrame,sum(is.na(myVariableName)))
myNaVector=rep(NA,10)