R help - Nov 2007 - Indexing and partially replacing 99, 999 in data frames

Dear WizaRds,

	unfortunately, I have been unable to replace the '99' and '999'
entries in

library(UsingR)
attach(babies)

as definitions for missing values NA, because sometimes the 99 entry is
indeed a correct value. Usually, or so I thought, NAs can
easily replace a, say, 999 entry via

mymat[mymat==999] <- "yodl"

in a matrix or data frame. Alas, the babies' dataset also includes 99
entries as true values. So, here is what I did:

#to remove all 999:
babies[babies==999] <- NA

, but to remove the 99 in columns nr. 10,12,17 I have come to a complete
stop. The corny idea of

babies$ht[babies$ht==99] <- NA
babies$dht[babies$dht==99] <- NA
babies$dwt[babies$dwt==99] <- NA

works, but seems to show that I have not really understood the art of
indexing, have I? The archives did not really offer enough insight for
me to solve the problem, I am ashamed.

I tried something with
babies[is.element(babies[,c(10,12,17)], 99)] <- NA # beeep, wrong or
babies[babies[,c(10,12,17)]==99] # no way, indeed.

detach(babies)

There must be a more intelligent and elegant solution.

Also, what is the nr. of rows after I remove all NA entries? Easy example:

frog <- matrix(1:42, ncol=3)
frog[sample(42, 7)] <- NA

length(frog[!is.na(frog)])
# ok, but I want to know the nr of rows without NAs
dim(frog[!is.na(frog),]) #no
nrow(!is.na(frog)) # no


Thank you for your help and
Cheers
mark

for you last case with 'frog':

sum(complete.cases(frog))


On Nov 24, 2007 11:52 AM, Mark Hempelmann <neo27 at rakers.de>
wrote:
>
> Dear WizaRds,
>
>        unfortunately, I have been unable to replace the '99' and
'999' entries in
>
> library(UsingR)
> attach(babies)
>
> as definitions for missing values NA, because sometimes the 99 entry is
> indeed a correct value. Usually, or so I thought, NAs can
> easily replace a, say, 999 entry via
>
> mymat[mymat==999] <- "yodl"
>
> in a matrix or data frame. Alas, the babies' dataset also includes 99
> entries as true values. So, here is what I did:
>
> #to remove all 999:
> babies[babies==999] <- NA
>
> , but to remove the 99 in columns nr. 10,12,17 I have come to a complete
> stop. The corny idea of
>
> babies$ht[babies$ht==99] <- NA
> babies$dht[babies$dht==99] <- NA
> babies$dwt[babies$dwt==99] <- NA
>
> works, but seems to show that I have not really understood the art of
> indexing, have I? The archives did not really offer enough insight for
> me to solve the problem, I am ashamed.
>
> I tried something with
> babies[is.element(babies[,c(10,12,17)], 99)] <- NA # beeep, wrong or
> babies[babies[,c(10,12,17)]==99] # no way, indeed.
>
> detach(babies)
>
> There must be a more intelligent and elegant solution.
>
> Also, what is the nr. of rows after I remove all NA entries? Easy example:
>
> frog <- matrix(1:42, ncol=3)
> frog[sample(42, 7)] <- NA
>
> length(frog[!is.na(frog)])
> # ok, but I want to know the nr of rows without NAs
> dim(frog[!is.na(frog),]) #no
> nrow(!is.na(frog)) # no
>
>
> Thank you for your help and
> Cheers
> mark
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


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

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