R help - Mar 2012 - Help: problem converting character to numeric

Dear R experts,
I have a dataframe imported from a csv file (with read.csv).

Here is an example:

yyyymm<- c("19860228",
"19860331","19860430","19860531")
id<-c("10000","10000","10000","10000")
re<- c("C","0.25", "0.98", "1.34")

mret<-data.frame(yyyymm, id, re)

mret<-as.numeric(as.character(mret$re))
Error: (converted from warning) NAs introduced by coercion


One of the column ("re" in the example above) has characters and
numbers,
but it should be treated a numeric column. Therefore, I want to eliminate
the rows in which the variable re has characters values (the first row in
the example).
In the past, I always used this code successfully (the characters were
replaced by NA, and only a warning message was issued). But now, I have an
error message and it no longer works. Could anyone suggest an alternative
way to do it?

Thanks a lot,
Best,
Aurelien

	[[alternative HTML version deleted]]

Dear Aurelien,

Thanks for the reproducible example.  Here is one way:

yyyymm<- c("19860228",
"19860331","19860430","19860531")
id<-c("10000","10000","10000","10000")
re<- c("C","0.25", "0.98", "1.34")
mret <- data.frame(yyyymm, id, re)
subset(mret, !is.na(as.numeric(as.character(re))))

HTH,
Jorge.-


On Wed, Mar 14, 2012 at 6:07 PM, Aurélien PHILIPPOT <> wrote:
> Dear R experts,
> I have a dataframe imported from a csv file (with read.csv).
>
> Here is an example:
>
> yyyymm<- c("19860228",
"19860331","19860430","19860531")
>
id<-c("10000","10000","10000","10000")
> re<- c("C","0.25", "0.98",
"1.34")
>
> mret<-data.frame(yyyymm, id, re)
>
> mret<-as.numeric(as.character(mret$re))
> Error: (converted from warning) NAs introduced by coercion
>
>
> One of the column ("re" in the example above) has characters and
numbers,
> but it should be treated a numeric column. Therefore, I want to eliminate
> the rows in which the variable re has characters values (the first row in
> the example).
> In the past, I always used this code successfully (the characters were
> replaced by NA, and only a warning message was issued). But now, I have an
> error message and it no longer works. Could anyone suggest an alternative
> way to do it?
>
> Thanks a lot,
> Best,
> Aurelien
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

On Wed, Mar 14, 2012 at 03:07:19PM -0700, Aur?lien PHILIPPOT
wrote:
> Dear R experts,
> I have a dataframe imported from a csv file (with read.csv).
> 
> Here is an example:
> 
> yyyymm<- c("19860228",
"19860331","19860430","19860531")
>
id<-c("10000","10000","10000","10000")
> re<- c("C","0.25", "0.98",
"1.34")
> 
> mret<-data.frame(yyyymm, id, re)
> 
> mret<-as.numeric(as.character(mret$re))
> Error: (converted from warning) NAs introduced by coercion
> 
> 
> One of the column ("re" in the example above) has characters and
numbers,
> but it should be treated a numeric column. Therefore, I want to eliminate
> the rows in which the variable re has characters values (the first row in
> the example).
> In the past, I always used this code successfully (the characters were
> replaced by NA, and only a warning message was issued). But now, I have an
> error message and it no longer works. Could anyone suggest an alternative
> way to do it?
Hi.

You probably have options(warn=2) set. This may be checked
using  getOption("warn"). If you set options(warn=0), then
the warning will not be converted to an error.

Hope this helps.

Petr Savicky.

On Wed, Mar 14, 2012 at 6:07 PM, Aur?lien PHILIPPOT
<aurelien.philippot at gmail.com> wrote:
> Dear R experts,
> I have a dataframe imported from a csv file (with read.csv).
>
> Here is an example:
>
> yyyymm<- c("19860228",
"19860331","19860430","19860531")
>
id<-c("10000","10000","10000","10000")
> re<- c("C","0.25", "0.98",
"1.34")
>
> mret<-data.frame(yyyymm, id, re)
>
> mret<-as.numeric(as.character(mret$re))
> Error: (converted from warning) NAs introduced by coercion
>
Check the value of the warn option:
> getOption("warn")
[1] 0
> as.numeric("C") # ok just gives warning
[1] NA
Warning message:
NAs introduced by coercion
> options(warn = 2)
> as.numeric("C") # now its an error
Error: (converted from warning) NAs introduced by coercion

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