R: Based on a vector with a word sequence, get n-grams (looking...

txt_previousgram {udpipe} | R Documentation

## Based on a vector with a word sequence, get n-grams (looking backward)

### Description

If you have annotated your text using `udpipe_annotate`, your text is tokenised in a sequence of words. Based on this vector of words in sequence getting n-grams comes down to looking at the previous word and the subsequent previous word andsoforth. These words can be `pasted` together to form an n-gram containing the second previous word, the previous word, the current word ...

### Usage

    txt_previousgram(x, n = 2, sep = " ")

### Arguments

`x` | a character vector where each element is just 1 term or word
`n` | an integer indicating the ngram. Values of 1 will keep the x, a value of 2 will append the previous term to the current term, a value of 3 will append the second previous term term and the previous term preceding the current term to the current term
`sep` | a character element indicating how to `paste` the subsequent words together

### Value

a character vector of the same length of `x` with the n-grams

### See Also

`paste`, `shift`

### Examples

    x <- sprintf("%s%s", LETTERS, 1:26)
    txt_previousgram(x, n = 2)

    data.frame(words = x,
               bigram = txt_previousgram(x, n = 2),
               trigram = txt_previousgram(x, n = 3, sep = "-"),
               quatrogram = txt_previousgram(x, n = 4, sep = ""),
               stringsAsFactors = FALSE)

    x <- c("A1", "A2", "A3", NA, "A4", "A5")
    data.frame(x,
               bigram = txt_previousgram(x, n = 2, sep = "_"),
               stringsAsFactors = FALSE)

[Package udpipe version 0.8.6 Index]