Develop R code

I need you to develop some software for me. I would like this software to be developed for Windows . I need to write a code in R language. Half of the code is already written I need to do a loop over months in a year to be more efficient. The other part is to write a code to find within a list of coordinates (x,y) which position falls inside a circle for which I have the coordinates corresponding to the center of the circle.