给定参数的格式问题

Question

I am trying to use textcat package for n-gram analysis, which has the following function:

textcat(x, p = TC_char_profiles, method = "CT", ..., options = list())

The function specification indicates that

The argument x can be a character vector of texts, or an R object which can be coerced to this using as.character.

I do not know what does the "R object which can be coerced to this using as.character" mean? In other words, I do not quite understand what should be the correct input format for this x in accordance with the above description. Suppose I have a 100 documents. How to transfer these documents into the format of x?

Answer 1

You really have two questions here.

(1). What does the "R object which can be coerced to this using as.character" mean?

That means that other classes of R object can be passed in, in place of one that is just character . An example is a factor, where as.character(x) will drop the extra features provided and revert to a simple character vector.

as.character(1:2) ## will give a vector c("1", "2")

This extends for other derived classes, and it's a standard R idiom to provide a method for common functions like as.character that define a coercion from any given class to character.

(2). In what format must my data be to input to textcat ?

In short, it must be a character vector or something that can be coerced to one . You are asking about documents, so presumably you have text files. The function readLines will provide a character vector from a text file, a vector as long as the number of lines in the file. Any more for this question needs a lot more detail from you about what the analysis is supposed to do, does it need to be broken into lines of text from a file? Broken into words? Keep sets of lines/words from different files as separate sets? And so on.

In really simplistic terms using the example in readLines , you could do something like this but further detail needs more information for your question:

 cat("TITLE extra line", "2 3 5 7", "", "11 13 17", file="ex.data",
     sep="\n")
 readLines("ex.data", n=-1)
 x <-      readLines("ex.data", n=-1)

 require(textcat)  
 textcat(x)