R help - Nov 2004 - Changing zeros to NAs in a data frame

Dear R People:

I have a data frame with some columns that are numeric and some which are 
factors.

There are zeros in the numeric columns and I would like to change them to 
NAs.  However, there are zeros in some of the factor columns, and I would 
like them to be left alone.

Is there a "global" way to do this, please?  I was thinking about use
the
results from "str" but am not sure.

R Version 2.0.0 Windows.

Thanks in advance.
Sincerely,
Laura Holt
mailto: lauraholt_983 at hotmail.com


Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963

Laura Holt wrote:
> Dear R People:
> 
> I have a data frame with some columns that are numeric and some which 
> are factors.
> 
> There are zeros in the numeric columns and I would like to change them 
> to NAs.  However, there are zeros in some of the factor columns, and I 
> would like them to be left alone.
> 
> Is there a "global" way to do this, please?  I was thinking about
use
> the results from "str" but am not sure.
> 
> R Version 2.0.0 Windows.
> 
Let x be your data.frame. Then use:

is.num <- sapply(x, is.numeric)
x[is.num] <- lapply(x[is.num], function(y) ifelse(y == 0, NA, y))

HTH,

--sundar

This isn't pretty but it's a way to do it:

foo <- data.frame(x = c(1,0,1,1,0,2,4), y = as.factor(c(0,2,1,1,0,3,1)))
Zero2NA <- function(x){
    if(is.numeric(x)) { x[x == 0] <- NA; }
    return(x)
}
foo2 <- as.data.frame(lapply(foo, Zero2NA))
foo
foo2

HTH, Andy

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Laura Holt
> Sent: Tuesday, November 16, 2004 11:31 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Changing zeros to NAs in a data frame
>
>
> Dear R People:
>
> I have a data frame with some columns that are numeric and some which are
> factors.
>
> There are zeros in the numeric columns and I would like to change them to
> NAs.  However, there are zeros in some of the factor columns, and I would
> like them to be left alone.
>
> Is there a "global" way to do this, please?  I was thinking about
use the
> results from "str" but am not sure.
>
> R Version 2.0.0 Windows.
>
> Thanks in advance.
> Sincerely,
> Laura Holt
> mailto: lauraholt_983 at hotmail.com
>
>
> Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963
>
> ______________________________________________
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> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>

On Tue, 16 Nov 2004, Laura Holt wrote:
> Dear R People:
>
> I have a data frame with some columns that are numeric and some which are 
> factors.
>
> There are zeros in the numeric columns and I would like to change them to 
> NAs.  However, there are zeros in some of the factor columns, and I would 
> like them to be left alone.
>
> Is there a "global" way to do this, please?  I was thinking about
use the
> results from "str" but am not sure.
myDF <- data.frame(a=0:4, b=letters[1:5], c=-2:2)
myDF[] <- lapply(myDF, function(x) if(is.numeric(x)) {x[x==0] <- NA; x}
else x)
> myDF
    a b  c
1 NA a -2
2  1 b -1
3  2 c NA
4  3 d  1
5  4 e  2


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595