R help - Apr 2016 - why data frame's logical index isnt working

data.frame.$columnToAdd["CurrentColumnName" ==
"ConditionMet"] <- 1

Can someone please explain to me why the above command gives all NAs to
columnToAdd?  I thought this was possible in R to do logical expression in
the index of a data frame

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you probably mean something like this

data.frame.$columnToAdd <- (data.frame.$CurrentColumnName
=data.frame.$ConditionMet)

what you did is compare two character strings.  They are not the same.
Therefore a new column
is created with the default value NA.
> tmp <- data.frame(A=1:4, B=c(1,3,4,5))
> tmp
  A B
1 1 1
2 2 3
3 3 4
4 4 5
> tmp$C <- tmp$A == tmp$B
> tmp
  A B     C
1 1 1  TRUE
2 2 3 FALSE
3 3 4 FALSE
4 4 5 FALSE
> tmp$D["A" == "B"] <- 1
> tmp
  A B     C  D
1 1 1  TRUE NA
2 2 3 FALSE NA
3 3 4 FALSE NA
4 4 5 FALSE NA
>
On Thu, Apr 7, 2016 at 9:46 PM, Michael Artz <michaeleartz at gmail.com>
wrote:
> data.frame.$columnToAdd["CurrentColumnName" ==
"ConditionMet"] <- 1
>
> Can someone please explain to me why the above command gives all NAs to
> columnToAdd?  I thought this was possible in R to do logical expression in
> the index of a data frame
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.

> On Apr 7, 2016, at 6:46 PM, Michael Artz <michaeleartz at gmail.com>
wrote:
> 
> data.frame.$columnToAdd["CurrentColumnName" ==
"ConditionMet"] <- 1
> 
> Can someone please explain to me why the above command gives all NAs to
> columnToAdd?  I thought this was possible in R to do logical expression in
> the index of a data frame
It is possible, but please execute this at a console line and then read
?"[" to see what is happening:

"CurrentColumnName" == "ConditionMet"  # almost surely FALSE

Let's assume your dataframe were named 'dat'.

Perhaps you meant to write:

dat$colToAdd[ dat[["CurrentColumnName"]] ==
dat[["ConditionMet"]] ] <- 1

And do please stop naming your dataframes "data.frame".

> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.
David Winsemius
Alameda, CA, USA

I don't get it, I thought the double index was to indicate and individual
element within a column(vector)?
I will stop using data.frame, thanks a lot!

On Thu, Apr 7, 2016 at 9:29 PM, David Winsemius <dwinsemius at
comcast.net>
wrote:
>
> > On Apr 7, 2016, at 6:46 PM, Michael Artz <michaeleartz at
gmail.com> wrote:
> >
> > data.frame.$columnToAdd["CurrentColumnName" ==
"ConditionMet"] <- 1
> >
> > Can someone please explain to me why the above command gives all NAs
to
> > columnToAdd?  I thought this was possible in R to do logical
expression
> in
> > the index of a data frame
>
> It is possible, but please execute this at a console line and then read
> ?"[" to see what is happening:
>
> "CurrentColumnName" == "ConditionMet"  # almost surely
FALSE
>
> Let's assume your dataframe were named 'dat'.
>
> Perhaps you meant to write:
>
> dat$colToAdd[ dat[["CurrentColumnName"]] ==
dat[["ConditionMet"]] ] <- 1
>
> And do please stop naming your dataframes "data.frame".
>
>
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > 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.
>
> David Winsemius
> Alameda, CA, USA
>
>
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