I want to export a matrix in R (and keep the names of both my rows and columns). When I use write.table or write.csv I get a matrix with a new column. How can I use this function.
Thank you for your help.
The R base function write. table() can be used to export a data frame or a matrix to a file. x: a matrix or a data frame to be written. file: a character specifying the name of the result file.
You don't get a new column, the row names are saved as a first column in the text file. So either you specify the column where the row names are given in read.table
, or use the row.names=FALSE
option in write.table
.
Demonstration :
mat <- matrix(1:10,ncol=2)
rownames(mat) <- letters[1:5]
colnames(mat) <- LETTERS[1:2]
mat
write.table(mat,file="test.txt") # keeps the rownames
read.table("test.txt",header=TRUE,row.names=1) # says first column are rownames
unlink("test.txt")
write.table(mat,file="test2.txt",row.names=FALSE) # drops the rownames
read.table("test.txt",header=TRUE)
unlink("test2.txt")
I assume that by "new column" you mean the row names that get written out by default. To suppress them, set row.names = FALSE
when calling write.table
or write.csv
.
write.table package:utils R Documentation
Data Output
Description:
‘write.table’ prints its required argument ‘x’ (after converting
it to a data frame if it is not one nor a matrix) to a file or
connection.
Usage:
write.table(x, file = "", append = FALSE, quote = TRUE, sep = " ",
eol = "\n", na = "NA", dec = ".", row.names = TRUE,
col.names = TRUE, qmethod = c("escape", "double"))
write.csv(...)
write.csv2(...)
...
row.names: either a logical value indicating whether the row names of
‘x’ are to be written along with ‘x’, or a character vector
of row names to be written.
col.names: either a logical value indicating whether the column names
of ‘x’ are to be written along with ‘x’, or a character
vector of column names to be written. See the section on
‘CSV files’ for the meaning of ‘col.names = NA’.
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