[R] Beginner's query - segmentation fault

[Laura Quinn]

thanks, have used

temp [temp==0]<- NA

and this seems to have worked, though it won't let me access individual
columns (ie temp$t1 etc) to work on - is there any real advantage in using
a matrix, or would i be better advised to deal with dataframes? (I have
double checked and temp is currently a matrix).



On Tue, 7 Oct 2003, Prof Brian Ripley wrote:

> On Tue, 7 Oct 2003, Laura Quinn wrote:
>
> > I am dealing with a huge matrix in R (20 columns, 54000 rows) and have
> > lots of missing values within the dataset which are currently displayed as
> > the value "-999.00" I am trying to create a new matrix (or change the
> > existing one) to display these values as "NA" so that I can then perform
> > the necessary analysis on the columns within the matrix.
> >
> > The matrix name is temp and the column names are t1 to t20 inclusive.
> >
> > I have tried the following command:
> >
> > temp$t1[temp$t1 == -999.00] <- NA
> >
> > and it returns a segmentation fault, can someone tell me what I am doing
> > wrong?
>
> Well, R should not segfault, so there is bug here somewhere.  However, I
> don't think what you have described can actually work. Is temp really a
> matrix?  If so temp$t1 will return NULL, and you should get an error
> message.
>
>
> If temp is a matrix
>
> temp[temp == -999.00] <- NA
>
> will do what you want.
>
>
> If as is more likely temp is a data frame with all columns numeric,
> there are several ways to do this, e.g.
>
> temp[] <- lapply(temp, function(x) ifelse(x == -999, NA, x))
>
> temp[as.matrix(temp) == -999] <- NA  # only in recent versions of R
>
> as well as explicit looping over columns.
>
> --
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>
>