R has a command-line editor which allows us to retrieve and edit commands we entered before. We also can install a command-line editor in Splus.

STEP 1

If you use Bourne, Korn, Bash or Z-Shell, type the following lines into your .bashrc file which is in your home directory:

export EDITOR="/usr/local/bin/vim" export S_CLEDITOR="/usr/local/bin/vim" export VISUAL="/usr/local/bin/vim"

If you use C-Shell or TC-Shell, then type the following lines into your .cshrc file which is in your home directory:

setenv EDITOR "/usr/local/bin/vim" setenv S_CLEDITOR "/usr/local/bin/vim" setenv VISUAL "/usr/local/bin/vim"

If you want to use emacs instead of vi, then simply replace the vim with emacs.

STEP 2

in your home directory, type command

source .bashrc

or

source .cshrc

STEP 3

type

Splus -e

to invoke editor when you enter into Splus session.

The most useful editing commands are summarized in the following table:

COMMAND emacs vi backward character Ctrl-B Esc, h forward character Ctrl-F Esc, l previous line Ctrl-P Esc, k next line Ctrl-N Esc, j beginning of line Ctrl-A Esc, ^ (Shift-6) end of line Ctrl-E Esc, $ (Shift-4) forward word Esc, f Esc, w backward word Esc, b Esc, b kill char Ctrl-D Esc, x kill line Ctrl-K Esc, Shift-d delete word Esc, d Esc, dw search backward Ctrl-R Esc, ? yank Ctrl-Y Esc, Shift-y transpose chars Ctrl-T Esc, xp

You can type Splus command

?Command.edit

to get the above table.

There are different versions of Splus installed in the department computing system. Splus is installed in Hajek, Newton, Emily, and Statlab. Splus 5 Splus 6 are installed in all servers.

• For Splus 3.4, the function to load the shared libraries is dyn.load.shared instead of dyn.load. The function dyn.load is used to load the object functions such as test.o obtained by using the command "g77 -c test.f". There is also no dyn.unload function in Splus 3.4.
• For Splus 5 and Splus 6, the function dyn.load and dyn.load.shared are obsolete. Splus 5 and Splus 6 use the function dyn.open to load the shared libraries and the function dyn.close to unload the shared libraries.

In R, we can call C functions. For example, we have the following toy C function in the file test.c.

/***** The function is to calculate Hadama product of two matrices. out[i][j]=x[i][j]*y[i][j]. The inputs x, y and the output out are vectors, not matrices. So in R, you need to transform input matrices into vectors and transform output vector back to matrix. *****/ void myHadamaProduct(double *x, double *y, int *nrow, int *ncol, double *out) { int i, j, r, c; r=*nrow; c=*ncol; for(i = 0; i < r; i ++) { for(j = 0; j < c; j ++) { out[i*c+j]=x[i*c+j]*y[i*c+j]; } } return; }

1. First, we need to compile the file test.c to create a shared library, test.so say, by using the GNU C compiler:
   gcc -fpic -shared -fno-gnu-linker -o test.so test.c
2. Next, we need to use the R function dyn.load to load the shared library test.so. if(!is.loaded("myHadamaProduct")){ dyn.load("./test.so") } The R function is.loaded is to check if the C function myHadamaProduct is already be loaded to R. If yes, then we do not need to loaded it again.
3. Next, we use the R function .C to call the C function myHadamaProduct. For example, x<-matrix(1:10,nrow=5, ncol=2) # get a 5x2 matrix y<-matrix(1:10,nrow=5, ncol=2) # get a 5x2 matrix # In R, a matrix is stored by column in the memory. # However, in C, a matrix is stored by row in the memory. # So we need to transpose the matrix x, namely t(x), before # transforming it to a vector. xx<-as.double(as.vector(t(x))) yy<-as.double(as.vector(t(y))) nr<-as.integer(nrow(x)) nc<-as.integer(ncol(x)) res<-.C("myHadamaProduct", xx, yy, nr, nc, out=as.double(rep(0.0, n))) # In C, matrix is stored by row. So when transforming back, we need to # specify byrow=T. mat<-matrix(res$out, ncol=nc, byrow=T) cat("Hadama product >>n") print(mat)
4. If you do not need to use the shared library test.so any more, you can use the R function dyn.unload to unload it. if(is.loaded("myHadamaProduct")){ dyn.unload("./test.so") }

Note:

• The C function called by R must be void type. For the example above, the function myHadamaProduct has to have the form: void myHadamaProduct(double *x, double *y, int *nrow, int *ncol, double *out) rather than double *myHadamaProduct(double *x, double *y, int *nrow, int *ncol)

  You have to let the function return values through arguments, e.g "double *out" in the above example. In fact if the arguments are pointers (e.g. *out) and you change their values they refer to within the function, then the values where the pointers refer to will be changed after calling this function.

• All arguments in the C function have to be passed by addresses instead of values. That is, all arguments have to be pointers. For the example above, you cannot change "int *nrow" to "int nrow".

  The values where the pointers refer to will be changed after calling the function, if the values are changed within the function. So be careful when using pointers as function arguments.

• Any values returned by C functions which are called in R must be initialized and must have the format: # if the variable is defined as double in the C function variablename=as.double(initialized values) # if the variable is defined as integer in the C function variablename=as.integer(initialized values) in the ".C" function (e.g. "out=as.double(rep(0.0, n))" in the above example).

  The input values must also be initialized and must have the above format. However, they can be formated before the ".C" function (e.g. "nr<-as.integer(nrow(x))" in the above example).

• If the output is not written as variablename=variablename format (e.g. out=as.double(rep(0.0, n)) in the above example), You still can get results. However, you have to use res[[5]] to refer out in the above example. In fact, the .C function return a list containing all arguments of the C function myHadamaProduct. Since out is the 5-th argument, you can use res[[5]] to refer to the 5-th elements of the list.
• It is okay that the file test.c contains the main function.
• Sometimes, the command "dyn.load("test.so")" gets error message. This is probably caused by the environment variable "$PATH" was not set correctly. You can either add the following line to the file ".bashrc" in your home directory: export PATH=$PATH:.:

  or use the command

  dyn.load("./test.so")