[R] setting a number of values to NA over a data.frame.

[John Kane]

--- Petr Pikal <petr.pikal at precheza.cz> wrote:

> Hi
> 
> Strange. It works for me without any problem.

The problem is that my dataframe has 1,s in about 50%
of the columns and I only want it to apply to a few
specified columns. My explanation may not have been
clear enough.

Using your example,I want all values for tio2 set to 1
but not any values in al2o3 whereas zeta[zeta==1]<-NA
is also changing al2o3[3] to NA.

Thanks

> 
> > zeta
>   tepl tio2 al2o3  iep
> 1   60    1   3.5 5.65
> 2   60    1   2.0 5.00
> 3   60    1   1.0 5.30
> 4   60    0   2.0 4.65
> 5   40    1   3.5 5.20
> 6   40    1   2.0 4.85
> 7   40    0   3.5 5.70
> 8   40    0   2.0 5.25
> > zeta[zeta==1]<-NA
> > zeta
>   tepl tio2 al2o3  iep
> 1   60   NA   3.5 5.65
> 2   60   NA   2.0 5.00
> 3   60   NA    NA 5.30
> 4   60    0   2.0 4.65
> 5   40   NA   3.5 5.20
> 6   40   NA   2.0 4.85
> 7   40    0   3.5 5.70
> 8   40    0   2.0 5.25
> 
> > str(zeta)
> 'data.frame':   8 obs. of  4 variables:
>  $ tepl : int  60 60 60 60 40 40 40 40
>  $ tio2 : num  NA NA NA 0 NA NA 0 0
>  $ al2o3: num  3.5 2 NA 2 3.5 2 3.5 2
>  $ iep  : num  5.65 5 5.3 4.65 5.2 4.85 5.7 5.25
> >
> 
> HTH
> Petr
> 
> 
> 
> On 7 Feb 2007 at 16:57, Erik Iverson wrote:
> 
> Date sent:      	Wed, 07 Feb 2007 16:57:40 -0600
> From:           	Erik Iverson
> <iverson at biostat.wisc.edu>
> To:             	John Kane <jrkrideau at yahoo.ca>
> Copies to:      	R R-help <r-help at stat.math.ethz.ch>
> Subject:        	Re: [R] setting a number of values
> to NA over  a data.frame.
> 
> > John -
> > 
> > Your initial problem uses 0, but the example uses
> 1 for the value that
> > gets an NA.  My solution uses 1 to fit with your
> example.  There may
> > be a better way, but try something like
> > 
> > data1[3:5] <- data.frame(lapply(data1[3:5],
> function(x) ifelse(x==1,
> > NA, x)))
> > 
> > The data1[3:5] is just a test subset  of columns I
> chose from your
> > data1 example.  Notice it appears twice, once on
> each side of the
> > assignment operator.
> > 
> > In English, apply to each column of the data frame
> (which is a list) a
> > function that will return NA if the element is 1,
> and the value
> > otherwise, and then turn the modified lists into a
> data.frame, and
> > save it as data1.
> > 
> > 
> > 
> > See the help files for lapply and ifelse if you
> haven't seen those
> > before.
> > 
> > Maybe someone has a better way?
> > 
> > Erik
> > 
> > John Kane wrote:
> > > This is probably a simple problem but I don't
> see a
> > > solution.
> > > 
> > > I have a data.frame with a number of columns
> where I
> > > would like 0 <- NA
> > > 
> > > thus I have df1[,144:157] <- NA if df1[, 144:
> 157] ==0
> > > and df1[, 190:198] <- NA if df1[, 190:198] ==0
> > > 
> > > but I cannot figure out a way do this.  
> > > 
> > > cata <- c( 1,1,6,1,1,NA)
> > > catb <- c( 1,2,3,4,5,6)
> > > doga <- c(3,5,3,6,4, 0)
> > > dogb <- c(2,4,6,8,10, 12)
> > > rata <- c (NA, 9, 9, 8, 9, 8)
> > > ratb <- c( 1,2,3,4,5,6)
> > > bata <- c( 12, 42,NA, 45, 32, 54)
> > > batb <- c( 13, 15, 17,19,21,23)
> > > id <- c('a', 'b', 'b', 'c', 'a', 'b')
> > > site <- c(1,1,4,4,1,4)
> > > mat1 <-  cbind(cata, catb, doga, dogb, rata,
> ratb,
> > > bata, batb)
> > > 
> > > data1 <- data.frame(site, id, mat1)
> > > data1
> > > 
> > >  # Obviously this works fine for one column
> > > 
> > > data1$site[data1$site ==1] <- NA  ; data1
> > > 
> > > but I cannot see how to do this with indices
> that
> > > would allow me to do more than one column in the
> > > data.frame.
> > > 
> > > At one point I even tried something like this
> > > a <- c("site")
> > > data1$a[data1$a ==1] <- NA
> > > 
> > > which seems to produce a corrupt data.frame.
> > > 
> > > I am sure it is simple but I don't see it.  
> > > 
> > > Any help would be much appreciated.
> > > 
> > > ______________________________________________
> > > R-help at stat.math.ethz.ch 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.
> > 
> > ______________________________________________
> > R-help at stat.math.ethz.ch 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.
> 
> Petr Pikal
> petr.pikal at precheza.cz
> 
>