Dear all, I would like to erase the content of a dataframe -- but not the dataframe itself -- in a simple and fast way. At the moment I do that by re-defining the dataframe itself in this way:> df <- data.frame(A = numeric(),+ B = numeric(), + C = character())> # assign > A <- 5 > B <- 0.6 > C <- 103 > # load > R <- cbind(A, B, C) > df <- rbind(df, R) > dfA B C 1 5 0.6 103> # erase > df <- data.frame(A = numeric(),+ B = numeric(), + C = character())> df[1] A B C <0 rows> (or 0-length row.names)>Is there a way to erase the content of the dataframe in a simplier (acting on all the dataframe at once instead of naming each column individually) and nicer (with a specific erasure command instead of re-defyining the object itself) way? Thank you. -- Best regards, Luigi
Hi Luigi, Maybe this: testdf<-data.frame(A=1,B=2,C=3)> testdfA B C 1 1 2 3 toNull<-function(x) return(NULL) testdf<-sapply(testdf,toNull) Jim On Thu, Sep 27, 2018 at 5:29 PM Luigi Marongiu <marongiu.luigi at gmail.com> wrote:> > Dear all, > I would like to erase the content of a dataframe -- but not the > dataframe itself -- in a simple and fast way. > At the moment I do that by re-defining the dataframe itself in this way: > > > df <- data.frame(A = numeric(), > + B = numeric(), > + C = character()) > > # assign > > A <- 5 > > B <- 0.6 > > C <- 103 > > # load > > R <- cbind(A, B, C) > > df <- rbind(df, R) > > df > A B C > 1 5 0.6 103 > > # erase > > df <- data.frame(A = numeric(), > + B = numeric(), > + C = character()) > > df > [1] A B C > <0 rows> (or 0-length row.names) > > > > Is there a way to erase the content of the dataframe in a simplier > (acting on all the dataframe at once instead of naming each column > individually) and nicer (with a specific erasure command instead of > re-defyining the object itself) way? > > Thank you. > -- > Best regards, > Luigi > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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.
Ah, yes, try 'as.data.frame" on it. Jim On Thu, Sep 27, 2018 at 6:00 PM Luigi Marongiu <marongiu.luigi at gmail.com> wrote:> > Thank you Jim, > this requires the definition of an ad hoc function; strange that R > does not have a function for this purpose... > Anyway, it works but it changes the structure of the data. By > redefining the dataframe as I did, I obtain: > > > df > [1] A B C > <0 rows> (or 0-length row.names) > > str(df) > 'data.frame': 0 obs. of 3 variables: > $ A: num > $ B: num > $ C: num > > When applying your function, I get: > > > df > $A > NULL > > $B > NULL > > $C > NULL > > > str(df) > List of 3 > $ A: NULL > $ B: NULL > $ C: NULL > > The dataframe has become a list. Would that affect downstream applications? > > Thank you, > Luigi > On Thu, Sep 27, 2018 at 9:45 AM Jim Lemon <drjimlemon at gmail.com> wrote: > > > > Hi Luigi, > > Maybe this: > > > > testdf<-data.frame(A=1,B=2,C=3) > > > testdf > > A B C > > 1 1 2 3 > > toNull<-function(x) return(NULL) > > testdf<-sapply(testdf,toNull) > > > > Jim > > On Thu, Sep 27, 2018 at 5:29 PM Luigi Marongiu <marongiu.luigi at gmail.com> wrote: > > > > > > Dear all, > > > I would like to erase the content of a dataframe -- but not the > > > dataframe itself -- in a simple and fast way. > > > At the moment I do that by re-defining the dataframe itself in this way: > > > > > > > df <- data.frame(A = numeric(), > > > + B = numeric(), > > > + C = character()) > > > > # assign > > > > A <- 5 > > > > B <- 0.6 > > > > C <- 103 > > > > # load > > > > R <- cbind(A, B, C) > > > > df <- rbind(df, R) > > > > df > > > A B C > > > 1 5 0.6 103 > > > > # erase > > > > df <- data.frame(A = numeric(), > > > + B = numeric(), > > > + C = character()) > > > > df > > > [1] A B C > > > <0 rows> (or 0-length row.names) > > > > > > > > > > Is there a way to erase the content of the dataframe in a simplier > > > (acting on all the dataframe at once instead of naming each column > > > individually) and nicer (with a specific erasure command instead of > > > re-defyining the object itself) way? > > > > > > Thank you. > > > -- > > > Best regards, > > > Luigi > > > > > > ______________________________________________ > > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > > > 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. > > > > -- > Best regards, > Luigi
Hm I would use> testdf<-data.frame(A=c(1,2),B=c(2,3),C=c(3,4)) > str(testdf)'data.frame': 2 obs. of 3 variables: $ A: num 1 2 $ B: num 2 3 $ C: num 3 4> testdf<-testdf[-(1:nrow(testdf)),] > str(testdf)'data.frame': 0 obs. of 3 variables: $ A: num $ B: num $ C: num Cheers Petr> -----Original Message----- > From: R-help <r-help-bounces at r-project.org> On Behalf Of Jim Lemon > Sent: Thursday, September 27, 2018 10:12 AM > To: Luigi Marongiu <marongiu.luigi at gmail.com>; r-help mailing list <r-help at r- > project.org> > Subject: Re: [R] Erase content of dataframe in a single stroke > > Ah, yes, try 'as.data.frame" on it. > > Jim > > On Thu, Sep 27, 2018 at 6:00 PM Luigi Marongiu <marongiu.luigi at gmail.com> > wrote: > > > > Thank you Jim, > > this requires the definition of an ad hoc function; strange that R > > does not have a function for this purpose... > > Anyway, it works but it changes the structure of the data. By > > redefining the dataframe as I did, I obtain: > > > > > df > > [1] A B C > > <0 rows> (or 0-length row.names) > > > str(df) > > 'data.frame': 0 obs. of 3 variables: > > $ A: num > > $ B: num > > $ C: num > > > > When applying your function, I get: > > > > > df > > $A > > NULL > > > > $B > > NULL > > > > $C > > NULL > > > > > str(df) > > List of 3 > > $ A: NULL > > $ B: NULL > > $ C: NULL > > > > The dataframe has become a list. Would that affect downstream > applications? > > > > Thank you, > > Luigi > > On Thu, Sep 27, 2018 at 9:45 AM Jim Lemon <drjimlemon at gmail.com> > wrote: > > > > > > Hi Luigi, > > > Maybe this: > > > > > > testdf<-data.frame(A=1,B=2,C=3) > > > > testdf > > > A B C > > > 1 1 2 3 > > > toNull<-function(x) return(NULL) > > > testdf<-sapply(testdf,toNull) > > > > > > Jim > > > On Thu, Sep 27, 2018 at 5:29 PM Luigi Marongiu > <marongiu.luigi at gmail.com> wrote: > > > > > > > > Dear all, > > > > I would like to erase the content of a dataframe -- but not the > > > > dataframe itself -- in a simple and fast way. > > > > At the moment I do that by re-defining the dataframe itself in this way: > > > > > > > > > df <- data.frame(A = numeric(), > > > > + B = numeric(), > > > > + C = character()) > > > > > # assign > > > > > A <- 5 > > > > > B <- 0.6 > > > > > C <- 103 > > > > > # load > > > > > R <- cbind(A, B, C) > > > > > df <- rbind(df, R) > > > > > df > > > > A B C > > > > 1 5 0.6 103 > > > > > # erase > > > > > df <- data.frame(A = numeric(), > > > > + B = numeric(), > > > > + C = character()) > > > > > df > > > > [1] A B C > > > > <0 rows> (or 0-length row.names) > > > > > > > > > > > > > Is there a way to erase the content of the dataframe in a simplier > > > > (acting on all the dataframe at once instead of naming each column > > > > individually) and nicer (with a specific erasure command instead > > > > of re-defyining the object itself) way? > > > > > > > > Thank you. > > > > -- > > > > Best regards, > > > > Luigi > > > > > > > > ______________________________________________ > > > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > > > > 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. > > > > > > > > -- > > Best regards, > > Luigi > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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.Osobn? ?daje: Informace o zpracov?n? a ochran? osobn?ch ?daj? obchodn?ch partner? PRECHEZA a.s. jsou zve?ejn?ny na: https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about processing and protection of business partner?s personal data are available on website: https://www.precheza.cz/en/personal-data-protection-principles/ D?v?rnost: Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a podl?haj? tomuto pr?vn? z?vazn?mu prohl??en? o vylou?en? odpov?dnosti: https://www.precheza.cz/01-dovetek/ | This email and any documents attached to it may be confidential and are subject to the legally binding disclaimer: https://www.precheza.cz/en/01-disclaimer/
You're right. Apparently one can form a list with NULL elements but not a data frame. I just saw Petr's answer, which seems to do the trick. Jim On Thu, Sep 27, 2018 at 6:19 PM Luigi Marongiu <marongiu.luigi at gmail.com> wrote:> > I am not sure if I got it right; Now I get: > > > toNull<-function(x) return(NULL) > > df<-as.data.frame(sapply(df,toNull)) > > df > data frame with 0 columns and 0 rows > > str(df) > 'data.frame': 0 obs. of 0 variables > On Thu, Sep 27, 2018 at 10:12 AM Jim Lemon <drjimlemon at gmail.com> wrote: > > > > Ah, yes, try 'as.data.frame" on it. > > > > Jim > > > > On Thu, Sep 27, 2018 at 6:00 PM Luigi Marongiu <marongiu.luigi at gmail.com> wrote: > > > > > > Thank you Jim, > > > this requires the definition of an ad hoc function; strange that R > > > does not have a function for this purpose... > > > Anyway, it works but it changes the structure of the data. By > > > redefining the dataframe as I did, I obtain: > > > > > > > df > > > [1] A B C > > > <0 rows> (or 0-length row.names) > > > > str(df) > > > 'data.frame': 0 obs. of 3 variables: > > > $ A: num > > > $ B: num > > > $ C: num > > > > > > When applying your function, I get: > > > > > > > df > > > $A > > > NULL > > > > > > $B > > > NULL > > > > > > $C > > > NULL > > > > > > > str(df) > > > List of 3 > > > $ A: NULL > > > $ B: NULL > > > $ C: NULL > > > > > > The dataframe has become a list. Would that affect downstream applications? > > > > > > Thank you, > > > Luigi > > > On Thu, Sep 27, 2018 at 9:45 AM Jim Lemon <drjimlemon at gmail.com> wrote: > > > > > > > > Hi Luigi, > > > > Maybe this: > > > > > > > > testdf<-data.frame(A=1,B=2,C=3) > > > > > testdf > > > > A B C > > > > 1 1 2 3 > > > > toNull<-function(x) return(NULL) > > > > testdf<-sapply(testdf,toNull) > > > > > > > > Jim > > > > On Thu, Sep 27, 2018 at 5:29 PM Luigi Marongiu <marongiu.luigi at gmail.com> wrote: > > > > > > > > > > Dear all, > > > > > I would like to erase the content of a dataframe -- but not the > > > > > dataframe itself -- in a simple and fast way. > > > > > At the moment I do that by re-defining the dataframe itself in this way: > > > > > > > > > > > df <- data.frame(A = numeric(), > > > > > + B = numeric(), > > > > > + C = character()) > > > > > > # assign > > > > > > A <- 5 > > > > > > B <- 0.6 > > > > > > C <- 103 > > > > > > # load > > > > > > R <- cbind(A, B, C) > > > > > > df <- rbind(df, R) > > > > > > df > > > > > A B C > > > > > 1 5 0.6 103 > > > > > > # erase > > > > > > df <- data.frame(A = numeric(), > > > > > + B = numeric(), > > > > > + C = character()) > > > > > > df > > > > > [1] A B C > > > > > <0 rows> (or 0-length row.names) > > > > > > > > > > > > > > > > Is there a way to erase the content of the dataframe in a simplier > > > > > (acting on all the dataframe at once instead of naming each column > > > > > individually) and nicer (with a specific erasure command instead of > > > > > re-defyining the object itself) way? > > > > > > > > > > Thank you. > > > > > -- > > > > > Best regards, > > > > > Luigi > > > > > > > > > > ______________________________________________ > > > > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > > > > > 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. > > > > > > > > > > > > -- > > > Best regards, > > > Luigi > > > > -- > Best regards, > Luigi