I found rmatio is a nice tool to convert data frame and list into .mat file (although it seems that the character is not supported), but in the following demo, I want to generate a nested list called data_list, but when I use write.mat to export it as a .mat file, only the first column of the data is reserved, see how can I solve such a problem? Thanks in advance.
library(rmatio)
data(iris)
iris
iris$group<-paste("group",rep(1:2,75),sep="")
names(iris)<-c('a','b','c','d','species','group')
## "."is not support as name in .mat file, so I rename it as "a b c d" for simplicity.
head(iris)
##split the data into list according to species.
out<-split(iris[,c(1:4,6)],f=iris$species)
out
##further split the data by group variable to create a nest list.
data_list<-lapply(out,function(x){
split(x,f=x$group)
})
write.mat(data_list, 'iris.mat')
After installing and loading Octave and learning a couple of commands and experimenting with the write.mat function, I have concluded that it does not handle nested lists. It apparently writes each item in a list to a separate variable in the matlab file. So if you want all of the data in iris (split into two groups) to go into a matlab file, and end up with separate variable written with rmatio you needs something like this:
iris$group <- 1:2
data_list <-
split(unlist(iris[1:4]), f=interaction(iris$Species, iris$group, rep(names(iris)[1:4], each=150)))
str(data_list)
write.mat(data_list, 'iris2.mat')
Then in an Octave session you see:
octave-3.4.0:19> load /Users/davidwinsemius/iris2.mat
octave-3.4.0:20> whos
Variables in the current scope:
Attr Name Size Bytes Class
==== ==== ==== ===== =====
setosa.1.Petal.Length 1x25 200 double
setosa.1.Petal.Width 1x25 200 double
setosa.1.Sepal.Length 1x25 200 double
setosa.1.Sepal.Width 1x25 200 double
setosa.2.Petal.Length 1x25 200 double
setosa.2.Petal.Width 1x25 200 double
setosa.2.Sepal.Length 1x25 200 double
setosa.2.Sepal.Width 1x25 200 double
versicolor.1.Petal.Length 1x25 200 double
versicolor.1.Petal.Width 1x25 200 double
versicolor.1.Sepal.Length 1x25 200 double
versicolor.1.Sepal.Width 1x25 200 double
versicolor.2.Petal.Length 1x25 200 double
versicolor.2.Petal.Width 1x25 200 double
versicolor.2.Sepal.Length 1x25 200 double
versicolor.2.Sepal.Width 1x25 200 double
virginica.1.Petal.Length 1x25 200 double
virginica.1.Petal.Width 1x25 200 double
virginica.1.Sepal.Length 1x25 200 double
virginica.1.Sepal.Width 1x25 200 double
virginica.2.Petal.Length 1x25 200 double
virginica.2.Petal.Width 1x25 200 double
virginica.2.Sepal.Length 1x25 200 double
virginica.2.Sepal.Width 1x25 200 double
Total is 600 elements using 4800 bytes
There was an R.matlab-package that did the transfer of the dataframe iris with a less Baroque process:
> require(R.matlab)
Loading required package: R.matlab
R.matlab v3.2.0 (2015-02-24) successfully loaded. See ?R.matlab for help.
Attaching package: ‘R.matlab’
The following objects are masked from ‘package:base’:
getOption, isOpen
> writeMat("iris3.mat", iris=iris, matVersion="5", onWrite=NULL, verbose=FALSE)
Which transferred a single object with 6 named columns.It was also able to transfer the data_list structure as a single item that had 24 columns.
octave-3.4.0:35> load /Users/davidwinsemius/dl.mat
octave-3.4.0:36> whos
Variables in the current scope:
Attr Name Size Bytes Class
==== ==== ==== ===== =====
data_list 1x1 4800 struct
iris 1x1 4800 struct
Total is 2 elements using 9600 bytes