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Wade Wall

2010-Dec-08 20:10 UTC

[R] evaluating NAs in a dataframe

Hi all,

How can one evaluate NAs in a numeric dataframe column?  For example, I have
a dataframe (demo) with a column of numbers and several NAs. If I write
demo.df >= 10, numerals will return TRUE or FALSE, but if the value is
"NA", "NA" is returned.  But if I write demo.df ==
"NA", it returns as "NA"
also.  I know that I can remove NAs, but would like to keep the dataframe as
is without creating a subset.  I basically want to add a line that evaluates
the NA in the demo dataframe.

As an example, I want to assign rows to classes based on values in
demo$Area. Some of the values in demo$Area are "NA"

for (i in 1:nrow(demo)) {
  if (demo$Area[i] > 0 && demo$Area[i] < 10)
{Class[i]<-"S01"} ## 1-10 cm2
  if (demo$Area[i] >= 10 && demo$Area[i] < 25) {Class[i] <-
"S02"} ##
10-25cm2
  if (demo$Area[i] >= 25 && demo$Area[i] < 50) {Class[i]
<-"S03"} ## 25-50
cm2
  if (demo$Area[i] >= 50 && demo$Area[i] < 100) {Class[i]
<-"S04"} ## 50-100
cm2
  if (demo$Area[i] >= 100 && demo$Area[i] < 200) {Class[i] <-
"S05"} ##
100-200 cm2
  if (demo$Area[i] >= 200 && demo$Area[i] < 400) {Class[i] <-
"S06"} ##
200-400 cm2
  if (demo$Area[i] >= 400 && demo$Area[i] < 800) {Class[i] <-
"S07"} ##
400-800 cm2
  if (demo$Area[i] >= 800 && demo$Area[i] < 1600) {Class[i] <-
"S08"} ##
800-1600 cm2
  if (demo$Area[i] >= 1600 && demo$Area[i] < 3200) {Class[i] <-
"S09"} ##
1600-3200 cm2
  if (demo$Area[i] >=3200) {Class[i] <- "S10"} ## >3200 cm2
  }

What happens is that I get the message "Error in if (demo$Area[i] > 0
&&
demo$Area[i] < 10) { : missing value where TRUE/FALSE needed"

Thanks for any help

Wade

	[[alternative HTML version deleted]]

Peter Ehlers

2010-Dec-08 20:46 UTC

head link

[R] evaluating NAs in a dataframe

On 2010-12-08 12:10, Wade Wall wrote:> Hi all,
>
> How can one evaluate NAs in a numeric dataframe column?  For example, I
have
> a dataframe (demo) with a column of numbers and several NAs. If I write
> demo.df>= 10, numerals will return TRUE or FALSE, but if the value is
> "NA", "NA" is returned.  But if I write demo.df ==
"NA", it returns as "NA"
> also.  I know that I can remove NAs, but would like to keep the dataframe
as
> is without creating a subset.  I basically want to add a line that
evaluates
> the NA in the demo dataframe.
>
> As an example, I want to assign rows to classes based on values in
> demo$Area. Some of the values in demo$Area are "NA"
>
> for (i in 1:nrow(demo)) {
>    if (demo$Area[i]>  0&&  demo$Area[i]<  10)
{Class[i]<-"S01"} ## 1-10 cm2
>    if (demo$Area[i]>= 10&&  demo$Area[i]<  25) {Class[i]<-
"S02"} ##
> 10-25cm2
>    if (demo$Area[i]>= 25&&  demo$Area[i]<  50)
{Class[i]<-"S03"} ## 25-50
> cm2
>    if (demo$Area[i]>= 50&&  demo$Area[i]<  100)
{Class[i]<-"S04"} ## 50-100
> cm2
>    if (demo$Area[i]>= 100&&  demo$Area[i]<  200)
{Class[i]<- "S05"} ##
> 100-200 cm2
>    if (demo$Area[i]>= 200&&  demo$Area[i]<  400)
{Class[i]<- "S06"} ##
> 200-400 cm2
>    if (demo$Area[i]>= 400&&  demo$Area[i]<  800)
{Class[i]<- "S07"} ##
> 400-800 cm2
>    if (demo$Area[i]>= 800&&  demo$Area[i]<  1600)
{Class[i]<- "S08"} ##
> 800-1600 cm2
>    if (demo$Area[i]>= 1600&&  demo$Area[i]<  3200)
{Class[i]<- "S09"} ##
> 1600-3200 cm2
>    if (demo$Area[i]>=3200) {Class[i]<- "S10"} ##>3200
cm2
>    }
>
> What happens is that I get the message "Error in if (demo$Area[i]> 
0&&
> demo$Area[i]<  10) { : missing value where TRUE/FALSE needed"
>You don't say what you want to have occur when x is NA. (I don't know
what 'evaluate NA' means.)

But why not just use something like:

  for(....){
    if(!is.na(x[i]){
      .... your stuff, preferably replacing '&&' with
'&' ....
    } else {....}
  }

Peter Ehlers
> Thanks for any help
>
> Wade
>

Philipp Pagel

2010-Dec-08 20:50 UTC

head link

[R] evaluating NAs in a dataframe

Hi!
> How can one evaluate NAs in a numeric dataframe column?  For example, I
have
> a dataframe (demo) with a column of numbers and several NAs. If I write
> demo.df >= 10, numerals will return TRUE or FALSE, but if the value is
> "NA", "NA" is returned. But if I write demo.df ==
"NA", it returns as "NA"
Sounds like you are looking for is.na :
> is.na(c(1,NA,3))[1] FALSE  TRUE FALSE

> As an example, I want to assign rows to classes based on values in
> demo$Area. Some of the values in demo$Area are "NA"
> 
> for (i in 1:nrow(demo)) {
>   if (demo$Area[i] > 0 && demo$Area[i] < 10)
{Class[i]<-"S01"} ## 1-10 cm2
>   if (demo$Area[i] >= 10 && demo$Area[i] < 25) {Class[i]
<- "S02"} ##
> 10-25cm2
[...]
>   if (demo$Area[i] >=3200) {Class[i] <- "S10"} ## >3200
cm2
>   }
> 
> What happens is that I get the message "Error in if (demo$Area[i] >
0 &&
> demo$Area[i] < 10) { : missing value where TRUE/FALSE needed"
First of all, you don't need a loop here. Example:

# make up some data
foo <- data.frame(a=sample(1:20, 20, replace=TRUE))
# assign to classes
foo$class <- cut(foo$a, breaks=c(-1, 7, 13, 20), labels=c('small',
'medium', 'large'))

This also works in the presence of NAs - but of course the class will
be NA in those cases which, at least in my opinion, is the correct
value.

cu
	Philipp

-- 
Dr. Philipp Pagel
Lehrstuhl f?r Genomorientierte Bioinformatik
Technische Universit?t M?nchen
Wissenschaftszentrum Weihenstephan
Maximus-von-Imhof-Forum 3
85354 Freising, Germany
http://webclu.bio.wzw.tum.de/~pagel/

Daniel Nordlund

2010-Dec-08 20:54 UTC

head link

[R] evaluating NAs in a dataframe

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
> On Behalf Of Wade Wall
> Sent: Wednesday, December 08, 2010 12:11 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] evaluating NAs in a dataframe
> 
> Hi all,
> 
> How can one evaluate NAs in a numeric dataframe column?  For example, I
> have
> a dataframe (demo) with a column of numbers and several NAs. If I write
> demo.df >= 10, numerals will return TRUE or FALSE, but if the value is
> "NA", "NA" is returned.  But if I write demo.df ==
"NA", it returns as
> "NA"
> also.  I know that I can remove NAs, but would like to keep the dataframe
> as
> is without creating a subset.  I basically want to add a line that
> evaluates
> the NA in the demo dataframe.
> 
> As an example, I want to assign rows to classes based on values in
> demo$Area. Some of the values in demo$Area are "NA"
> 
> for (i in 1:nrow(demo)) {
>   if (demo$Area[i] > 0 && demo$Area[i] < 10)
{Class[i]<-"S01"} ## 1-10 cm2
>   if (demo$Area[i] >= 10 && demo$Area[i] < 25) {Class[i]
<- "S02"} ##
> 10-25cm2
>   if (demo$Area[i] >= 25 && demo$Area[i] < 50) {Class[i]
<-"S03"} ## 25-50
> cm2
>   if (demo$Area[i] >= 50 && demo$Area[i] < 100) {Class[i]
<-"S04"} ## 50-
> 100
> cm2
>   if (demo$Area[i] >= 100 && demo$Area[i] < 200) {Class[i]
<- "S05"} ##
> 100-200 cm2
>   if (demo$Area[i] >= 200 && demo$Area[i] < 400) {Class[i]
<- "S06"} ##
> 200-400 cm2
>   if (demo$Area[i] >= 400 && demo$Area[i] < 800) {Class[i]
<- "S07"} ##
> 400-800 cm2
>   if (demo$Area[i] >= 800 && demo$Area[i] < 1600) {Class[i]
<- "S08"} ##
> 800-1600 cm2
>   if (demo$Area[i] >= 1600 && demo$Area[i] < 3200) {Class[i]
<- "S09"} ##
> 1600-3200 cm2
>   if (demo$Area[i] >=3200) {Class[i] <- "S10"} ## >3200
cm2
>   }
> 
> What happens is that I get the message "Error in if (demo$Area[i] >
0 &&
> demo$Area[i] < 10) { : missing value where TRUE/FALSE needed"
> 
> Thanks for any help
> 
> Wade
> 
Wade,

As you have discovered, you need to test for NA first, and to do that you need
to use is.na().  Something like this should work

for (i in 1:nrow(demo)) {
  if (is.na(demo$Area[i])) Class[i] <- "Sna" else
  if (demo$Area[i] < 10) Class[i] <- "S01"   else 
  if (demo$Area[i] < 25) Class[i] <- "S02"   else
  if (demo$Area[i] < 50) Class[i] <- "S03"   else 
  if (demo$Area[i] < 100) Class[i] <- "S04"  else 
  if (demo$Area[i] < 200) Class[i] <- "S05"  else 
  if (demo$Area[i] < 400) Class[i] <- "S06"  else 
  if (demo$Area[i] < 800) Class[i] <- "S07"  else 
  if (demo$Area[i] < 1600) Class[i] <- "S08" else 
  if (demo$Area[i] < 3200) Class[i] <- "S09" else 
  Class[i] <- "S10" 
  }

Hope this is helpful,

Dan

Daniel Nordlund
Bothell, WA USA

David Winsemius

2010-Dec-08 21:19 UTC

head link

[R] evaluating NAs in a dataframe

On Dec 8, 2010, at 3:10 PM, Wade Wall wrote:
> Hi all,
>
> How can one evaluate NAs in a numeric dataframe column?  For  
> example, I have
> a dataframe (demo) with a column of numbers and several NAs. If I  
> write
> demo.df >= 10, numerals will return TRUE or FALSE, but if the value is
> "NA", "NA" is returned.  But if I write demo.df ==
"NA", it returns
> as "NA"
> also.  I know that I can remove NAs, but would like to keep the  
> dataframe as
> is without creating a subset.  I basically want to add a line that  
> evaluates
> the NA in the demo dataframe.
That looks really, really painful. Why not use the function  
findInterval and then do a lookup in a character vector. Then you can  
throw away that loopy construct completely.

 > demo  <- data.frame(Area = runif(10, 0, 100))
 > demo$catarea <- findInterval(demo$Area, c(0,25,50,75,100))
 > demo
         Area catarea
1  71.440401       3
2   8.438097       1
3  45.492178       2
4  50.669996       3
5  15.444114       1
6  33.954948       2
7  19.738747       1
8  56.485654       3
9  29.218921       2
10 74.204611       3
 > demo$catname <- c("S01","S02",
"S03","S04")[demo$catarea]
 > demo
         Area catarea catname
1  71.440401       3     S03
2   8.438097       1     S01
3  45.492178       2     S02
4  50.669996       3     S03
5  15.444114       1     S01
6  33.954948       2     S02
7  19.738747       1     S01
8  56.485654       3     S03
9  29.218921       2     S02
10 74.204611       3     S03

-- 
David.>
> As an example, I want to assign rows to classes based on values in
> demo$Area. Some of the values in demo$Area are "NA"
>
> for (i in 1:nrow(demo)) {
>  if (demo$Area[i] > 0 && demo$Area[i] < 10)
{Class[i]<-"S01"} ##
> 1-10 cm2
>  if (demo$Area[i] >= 10 && demo$Area[i] < 25) {Class[i] <-
"S02"} ##
> 10-25cm2
>  if (demo$Area[i] >= 25 && demo$Area[i] < 50) {Class[i]
<-"S03"} ##
> 25-50
> cm2
>  if (demo$Area[i] >= 50 && demo$Area[i] < 100) {Class[i]
<-"S04"} ##
> 50-100
> cm2
>  if (demo$Area[i] >= 100 && demo$Area[i] < 200) {Class[i]
<- "S05"} ##
> 100-200 cm2
>  if (demo$Area[i] >= 200 && demo$Area[i] < 400) {Class[i]
<- "S06"} ##
> 200-400 cm2
>  if (demo$Area[i] >= 400 && demo$Area[i] < 800) {Class[i]
<- "S07"} ##
> 400-800 cm2
>  if (demo$Area[i] >= 800 && demo$Area[i] < 1600) {Class[i]
<- "S08"}
> ##
> 800-1600 cm2
>  if (demo$Area[i] >= 1600 && demo$Area[i] < 3200) {Class[i]
<-
> "S09"} ##
> 1600-3200 cm2
>  if (demo$Area[i] >=3200) {Class[i] <- "S10"} ## >3200
cm2
>  }
>
> What happens is that I get the message "Error in if (demo$Area[i] >
> 0 &&
> demo$Area[i] < 10) { : missing value where TRUE/FALSE needed"
>
> Thanks for any help
>
> Wade
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT

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