R help - Jul 2005 - column-wise deletion in data-frames

Hi,

I have a huge dataframe and like to delete all those variables from it that that
have NAs. The deletion of vars should be done column-wise, and not row-wise as
na.omit would do it, because I have some vars that have NAs for all rows thus
using na.omit I would end up with no obs. Is there a convenient way to do this
R?

To make the question more explicit. Imagine a dataset that looks something like
this (but much bigger)

X1 <- rnorm(1000)
X2 <- c(rep(NA,1000))
X3 <- rnorm(1000)
X4 <- c(rep(NA,499),1,44,rep(NA,499))
X5 <- rnorm(1000)

data <- as.data.frame(cbind(X1,X2,X3,X4,X5))

So only X1, X3 and X5 are vars without any NAs and there are some vars (X2 and
X4 stacked in between that have NAs). Now, how can I extract those former vars
in a new dataset or remove all those latter vars in between that have NAs
(without missing a single row)?

Thank you very much!

Best,
jens

jhainm at fas.harvard.edu wrote:
> Hi,
> 
> I have a huge dataframe and like to delete all those variables from it that
that
> have NAs. The deletion of vars should be done column-wise, and not row-wise
as
> na.omit would do it, because I have some vars that have NAs for all rows
thus
> using na.omit I would end up with no obs. Is there a convenient way to do
this
> R?
> 
> To make the question more explicit. Imagine a dataset that looks something
like
> this (but much bigger)
> 
> X1 <- rnorm(1000)
> X2 <- c(rep(NA,1000))
> X3 <- rnorm(1000)
> X4 <- c(rep(NA,499),1,44,rep(NA,499))
> X5 <- rnorm(1000)
> 
> data <- as.data.frame(cbind(X1,X2,X3,X4,X5))
> 
> So only X1, X3 and X5 are vars without any NAs and there are some vars (X2
and
> X4 stacked in between that have NAs). Now, how can I extract those former
vars
> in a new dataset or remove all those latter vars in between that have NAs
> (without missing a single row)?
> ...
   Someone else will probably suggest something more elegant, but how 
about this:

newdata <- data[,-which(apply(data, 2, function(x){all(is.na(x))}))]

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