R help - Aug 2013 - decimal separator from comma to dot

This is my reproducible example

df<-structure(list(IDANT = c(37837L, 37838L, 37839L, 37840L, 37841L, 
37842L, 37843L, 40720L, 40721L, 40722L), N_TX = c(6L, 6L, 6L, 
4L, 1L, 1L, 1L, 2L, 2L, 1L), TILT = c(0L, 0L, 0L, 0L, 6L, 6L, 
6L, 0L, 0L, 0L), DIREZIONE = c(50L, 220L, 110L, 50L, 220L, 110L, 
50L, 170L, 70L, 270L), DATA_INI = structure(c(2L, 2L, 2L, 2L, 
2L, 2L, 2L, 1L, 1L, 1L), .Label = c("20/10/2004",
"29/08/2002"
), class = "factor"), POT_TX = structure(c(4L, 4L, 4L, 3L, 2L, 
2L, 2L, 1L, 1L, 1L), .Label = c("10", "11,5", "4",
"8"), class = "factor")),
.Names = c("IDANT", 
"N_TX", "TILT", "DIREZIONE", "DATA_INI",
"POT_TX"), row.names = c(NA,
10L), class = "data.frame")

The data frame ?df? it?s a ?simplified snapshot? from an oracle table
imported via odbc (by using the package RODBC) ;
now, the problem with the data frame ?df? is that one variable ?POT_TX? have
the decimal separator formatted with comma instead of dot; 
so I?m in the need to reformat the variable from factor to numeric type to
perform some useful calculations

this is my code I worked so far

#function to change comma to dot
myfun <- function(x) {sub(",",".",x)}

#apply the function to all variables
new <- apply(df, 2, myfun )
newdf <- data.frame(apply(new, 2, as.numeric))
str(newdf)

#apply the function to one variables
var<-as.numeric(sapply(df[,6], FUN=myfun))
df$POT_TX<-var
str(df)


my questions:

1.	is it possible to use the more convenient function ?apply? with reference
to just some variables and not all of them? I?ve been reading on the help
that ?Where X has named dimnames, it can be a character vector selecting
dimension names.?, what does exactly means that?

2.	do you know some more convenient methods to perform comma to dot
substitution in just some selected variables of a data frame? To note that
the desired final result is again a dataframe

3.	do you know any workaround to set the decimal delimiter for a variable
(field) ?at the early steps? when connecting via odbc and then querying to
the table?
For these ?early steps? I?ve been using something like:
library(RODBC)
con<-odbcConnect("dsn", uid="user",
pwd="password")
df<-sqlQuery(con, "select * from table.name;")

thank you all for the eventual support




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Hi,

I think this could help you:
https://stat.ethz.ch/pipermail/r-help/2008-January/152378.html

Best

Simon

On Aug 9, 2013, at 12:19 PM, maxbre <mbressan at arpa.veneto.it> wrote:
> This is my reproducible example
> 
> df<-structure(list(IDANT = c(37837L, 37838L, 37839L, 37840L, 37841L, 
> 37842L, 37843L, 40720L, 40721L, 40722L), N_TX = c(6L, 6L, 6L, 
> 4L, 1L, 1L, 1L, 2L, 2L, 1L), TILT = c(0L, 0L, 0L, 0L, 6L, 6L, 
> 6L, 0L, 0L, 0L), DIREZIONE = c(50L, 220L, 110L, 50L, 220L, 110L, 
> 50L, 170L, 70L, 270L), DATA_INI = structure(c(2L, 2L, 2L, 2L, 
> 2L, 2L, 2L, 1L, 1L, 1L), .Label = c("20/10/2004",
"29/08/2002"
> ), class = "factor"), POT_TX = structure(c(4L, 4L, 4L, 3L, 2L, 
> 2L, 2L, 1L, 1L, 1L), .Label = c("10", "11,5",
"4", "8"), class = "factor")),
> .Names = c("IDANT", 
> "N_TX", "TILT", "DIREZIONE",
"DATA_INI", "POT_TX"), row.names = c(NA,
> 10L), class = "data.frame")
> 
> The data frame ?df? it?s a ?simplified snapshot? from an oracle table
> imported via odbc (by using the package RODBC) ;
> now, the problem with the data frame ?df? is that one variable ?POT_TX?
have
> the decimal separator formatted with comma instead of dot; 
> so I?m in the need to reformat the variable from factor to numeric type to
> perform some useful calculations
> 
> this is my code I worked so far
> 
> #function to change comma to dot
> myfun <- function(x) {sub(",",".",x)}
> 
> #apply the function to all variables
> new <- apply(df, 2, myfun )
> newdf <- data.frame(apply(new, 2, as.numeric))
> str(newdf)
> 
> #apply the function to one variables
> var<-as.numeric(sapply(df[,6], FUN=myfun))
> df$POT_TX<-var
> str(df)
> 
> 
> my questions:
> 
> 1.	is it possible to use the more convenient function ?apply? with
reference
> to just some variables and not all of them? I?ve been reading on the help
> that ?Where X has named dimnames, it can be a character vector selecting
> dimension names.?, what does exactly means that?
> 
> 2.	do you know some more convenient methods to perform comma to dot
> substitution in just some selected variables of a data frame? To note that
> the desired final result is again a dataframe
> 
> 3.	do you know any workaround to set the decimal delimiter for a variable
> (field) ?at the early steps? when connecting via odbc and then querying to
> the table?
> For these ?early steps? I?ve been using something like:
> library(RODBC)
> con<-odbcConnect("dsn", uid="user",
pwd="password")
> df<-sqlQuery(con, "select * from table.name;")
> 
> thank you all for the eventual support
> 
> 
> 
> 
> --
> View this message in context:
http://r.789695.n4.nabble.com/decimal-separator-from-comma-to-dot-tp4673414.html
> Sent from the R help mailing list archive at Nabble.com.
> 
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.