[R] Seeking help in Package development

[Nipesh Bajaj]

Dear all, I am a new user of R and currently trying hard to develop my
own package. Here I am following this tutorial
'http://www.mathfinance.cn/how-to-create-an-R-package-in-windows/'

Here it says that (step 8): "open a “command prompt” window, change
the directory to where your package is, type the command “R CMD build
MonteCarloPi” to build the package, this will generate a file called
MonteCarloPi_1.0.tar.gz. "

According to that, I have opened the Windows command prompt window (a
black screen window) and then changed the directory, where my new
package (a folder in current working directory in R, as created by
'package.skeleton') is there. Then typed 'R CMD build MyPackage' (I
named my package as 'MyPackage'). However doing so I got following
error in that command prompt:

'R' is not recognized as an internal or external command, operable
program or batch file.

Can somebody please guide me what to do in this situation?

Best thanks