Embedding R in Windows applications, and executing R remotely

R is object oriented, and objects are the standard way of packing analysis results in R. Many programming environments and applications programs in Windows can act as as (D)COM clients, which is the standard way of accessing objects exposed by (D)COM servers. Particularly, all Microsoft office programs are (D)COM clients and therefore can access any (D)COM server. Therefore, in encapsulating R as a (D)COM server is a natural choice to make R functionality accessible to other programs. To embed R in other programs, therefore, one of the key questions is what kind of objects are exposed to these applications hosting R, and how these objects are exposed. There are two different routes that can be taken here. We can either choose to expose R objects “as is”, with all their richness, or we can choose a minimalist approach and only offer objects of types which can be handled easily by programs which normally do not employ rich object types for the data they usually handle. The difference can be very well illustrated when R is embedded in Excel. A spreadsheet essentially has 6 data types, scalars, vectors, and matrices of either numbers or strings. If we want to make R functionality a part of the spreadsheet functionality, it is sufficient that the R (D)COM server exposed this type od data objects. On the other hand, VBA (the programming language built into Excel) allows to work with any type of object. Therefore, the whole R object model, and even user-defined new object types, can be made accessible in VBA, and therefore be used in Excel. The question is, how is R being used in connection with Excel. When the programmes “thinks R” and uses Excel just as a convenient data source and data editor, the full object model makes sense. Then, programming is done in R and VBA, and data and results are just transferred from time to time between worksheets and R. This way, Excel becomes a convenience item for R, but conceptually R is the center of the programming model. If we want to use R as an extension of Excel worksheets, and only as subroutines accessible from VBA, the minimalist approach seems more adapted. In