如何使用本機R創建文檔術語矩陣

我想使用本機R創建文檔術語矩陣（無需額外的插件，例如tm）。如何使用本機R創建文檔術語矩陣

Doc1: the test was to test the test 
Doc2: we did prepare the exam to test the exam 
Doc3: was the test the exam 
Doc4: the exam we did prepare was to test the test 
Doc5: we were successful so we all passed the exam

我想達到如下：

  Term Doc1 Doc2 Doc3 Doc4 Doc5 DF 
1   all 0 0 0 0 1 1 
2   did 0 1 0 1 0 2 
3  exam 0 2 1 1 1 4 
4  passed 0 0 0 0 1 1

來源

2013-10-25 Simon Kofler

你可以從'tm'軟件包中查看源代碼並重寫它......爲什麼你不想使用現成的工具？ – Justin

我首先看看已經存在的函數的源代碼。 – David

這裏有一個方法，但是又爲什麼不使用TM包中的數據結構如下？

## Your data 
## dat <- structure(list(person = structure(1:5, .Label = c("Doc1", "Doc2", 
##  "Doc3", "Doc4", "Doc5"), class = "factor"), 
##  text = c("the test was to test the test", 
##  "we did prepare the exam to test the exam", "was the test the exam", 
##  "the exam we did prepare was to test the test", 
##  "we were successful so we all passed the exam" 
## )), .Names = c("doc", "text"), class = "data.frame", row.names = c(NA, 
##  -5L)) 

## Function to turn list of vects into sparse matrix 
mtabulate <- function(vects) { 
    lev <- sort(unique(unlist(vects))) 
    dat <- do.call(rbind, lapply(vects, function(x, lev){ 
     tabulate(factor(x, levels = lev, ordered = TRUE), 
     nbins = length(lev))}, lev = lev)) 
    colnames(dat) <- sort(lev) 
    data.frame(dat, check.names = FALSE) 
} 


out <- lapply(split(dat$text, dat$doc), function(x) { 
    unlist(strsplit(tolower(x), " ")) 
}) 

t(mtabulate(out)) 

##   Doc1 Doc2 Doc3 Doc4 Doc5 
## all   0 0 0 0 1 
## did   0 1 0 1 0 
## exam   0 2 1 1 1 
## passed  0 0 0 0 1 
## prepare  0 1 0 1 0 
## so   0 0 0 0 1 
## successful 0 0 0 0 1 
## test   3 1 1 2 0 
## the   2 2 2 2 1 
## to   1 1 0 1 0 
## was   1 0 1 1 0 
## we   0 1 0 1 2 
## were   0 0 0 0 1

來源

2013-10-25 15:47:37

對DF列使用'rowSums'。 –

如何使用本機R創建文檔術語矩陣

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