R help - Jan 2010 - how to handle missing values "." when importing data in R

hi, I have a question about importing data in R.

I want to import a file which has missing value in it, and the missing
values are denoted as ".", I want to first read in the file, and then
change
the "." into the number zero "0".

how can I do that?

thank you,

karena
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?read.table

na.strings='.'

Then change all NAs to zero     df$col[is.na(df$col)] <- 0

On Tue, Jan 12, 2010 at 12:46 PM, karena <dr.jzhou@gmail.com> wrote:
>
> hi, I have a question about importing data in R.
>
> I want to import a file which has missing value in it, and the missing
> values are denoted as ".", I want to first read in the file, and
then
> change
> the "." into the number zero "0".
>
> how can I do that?
>
> thank you,
>
> karena
> --
> View this message in context:
>
http://n4.nabble.com/how-to-handle-missing-values-when-importing-data-in-R-tp1012298p1012298.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
>
http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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On 12-Jan-10 17:46:47, karena wrote:
> hi, I have a question about importing data in R.
> 
> I want to import a file which has missing value in it, and the missing
> values are denoted as ".", I want to first read in the file, and
then
> change the "." into the number zero "0".
> 
> how can I do that?
> 
> thank you,
> 
> karena
It may depend on what format the file is in, but if it is a tabular
text file or a CSV file then you can use the "na.strings" parameter.
Here is an example of a little CSV file with "." used for
"missing":

file temp.csv:
--------------
A,B,C,D
1.1,1.2,1.3,1.4
2.1,2.2,.,2.4
3.1,.,3.3,3.4
4.1,.,.,4.4

  D <- read.csv("temp.csv",na.strings=".")
  D
  #     A   B   C   D
  # 1 1.1 1.2 1.3 1.4
  # 2 2.1 2.2  NA 2.4
  # 3 3.1  NA 3.3 3.4
  # 4 4.1  NA  NA 4.4

So the "." have gone in as NA (the right thing to do in the first
instance with missing data). Now you can replace these by zeros:

  D[is.na(D)] <- 0
  D
  # 1 1.1 1.2 1.3 1.4
  # 2 2.1 2.2 0.0 2.4
  # 3 3.1 0.0 3.3 3.4
  # 4 4.1 0.0 0.0 4.4

Ted.

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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
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Date: 12-Jan-10                                       Time: 18:42:40
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