thanks, have used
temp [temp==0]<- NA
Please use is.na(temp[temp==0]) <- TRUE
and this seems to have worked, though it won't let me access individual
columns (ie temp$t1 etc)
No! temp$t1 is a list element or column of a data.frame, but not a column of a matrix. *PLEASE*, read manuals, help pages, or books on R how to use index / extract elements.
Please read my previous answer on how to access individual columns.
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).
Working on matrices is supposed to be faster. But matrices have the restriction of one data type for all columns (e.g. numeric).
Uwe Ligges
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, [EMAIL PROTECTED] 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
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