write.table and read.table commands
On Aug 27, 2012, at 10:04 PM, R. Michael Weylandt <michael.weylandt at gmail.com
> wrote:
It's because read.table returns a data frame, not a matrix. You can coerce to a matrix with as.matrix() but you might loose information if your variables are of different classes. Michael On Aug 27, 2012, at 7:07 PM, Cheryl Johnson <johnson.cheryl625 at gmail.com
wrote:
Greetings,
When I try to use the write.table command to save a matrix as a
file and
then open the file with read.table, if I try to take the mean of
the entire
matrix, instead each column of the matrix has its mean calculated.
I have
copied and pasted an example of my code below. When I try to make the
header false with the read.table command, I am given an error
message. I
would appreciate any guidance for how to average the entire matrix
instead
of just the columns.
Thanks
z=matrix(1:20,4,5)
write.table(z,
file="exercise.csv",sep=",",col.names=NA,qmethod="double")
j=read.table("exercise.csv",header=T,sep=",",row.names=1)
mean(j)
V1 V2 V3 V4 V5
2.5 6.5 10.5 14.5 18.5
Warning message:
mean(<data.frame>) is deprecated.
Use colMeans() or sapply(*, mean) instead.
Notice that the error message was telling you that there was a
`mean.data.frame` function which is slated for removal (perhaps) in
the next version of R.
You can read about its behavior:
?mean.data.frame
You could have gotten the desired behavior with:
mean(mean(j))
Or by saving the z object and load it as an Rdata file.
Or with
> z=matrix(1:20,4,5)
> write.table(z, file="exercise.csv",sep=",",row.names=FALSE,
col.names=FALSE)
> j=scan("exercise.csv",sep=",", what=double())
Read 20 items
> mean(j)
[1] 10.5
(Although the numbers are now in a vector.)
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David Winsemius, MD Alameda, CA, USA