A basic example for the usage of the quanteda package

The following makes use of the quanteda package. You may need to install it from CRAN using the code install.packages("quanteda") if you want to run this on your computer. (The package is already installed on the notebook container, however.)

library(quanteda)

Package version: 3.2.1
Unicode version: 13.0
ICU version: 67.1
Parallel computing: 20 of 20 threads used.
See https://quanteda.io for tutorials and examples.

quanteda_options(print_corpus_max_ndoc=3)

# This is an example corpus contained in the 'quanteda' package
data_corpus_inaugural

Corpus consisting of 59 documents and 4 docvars.
1789-Washington :
"Fellow-Citizens of the Senate and of the House of Representa..."

1793-Washington :
"Fellow citizens, I am again called upon by the voice of my c..."

1797-Adams :
"When it was first perceived, in early times, that no middle ..."

[ reached max_ndoc ... 56 more documents ]

mode(data_corpus_inaugural)

[1] "character"

class(data_corpus_inaugural)

[1] "corpus"    "character"

data_corpus_inaugural[1:3]

Corpus consisting of 3 documents and 4 docvars.
1789-Washington :
"Fellow-Citizens of the Senate and of the House of Representa..."

1793-Washington :
"Fellow citizens, I am again called upon by the voice of my c..."

1797-Adams :
"When it was first perceived, in early times, that no middle ..."

str(docvars(data_corpus_inaugural))

'data.frame':	59 obs. of  4 variables:
 $ Year     : int  1789 1793 1797 1801 1805 1809 1813 1817 1821 1825 ...
 $ President: chr  "Washington" "Washington" "Adams" "Jefferson" ...
 $ FirstName: chr  "George" "George" "John" "Thomas" ...
 $ Party    : Factor w/ 6 levels "Democratic","Democratic-Republican",..: 4 4 3 2 2 2 2 2 2 2 ...

docvars(data_corpus_inaugural,"Year")

 [1] 1789 1793 1797 1801 1805 1809 1813 1817 1821 1825 1829 1833 1837 1841 1845
[16] 1849 1853 1857 1861 1865 1869 1873 1877 1881 1885 1889 1893 1897 1901 1905
[31] 1909 1913 1917 1921 1925 1929 1933 1937 1941 1945 1949 1953 1957 1961 1965
[46] 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 2017 2021

data_corpus_inaugural$Year

 [1] 1789 1793 1797 1801 1805 1809 1813 1817 1821 1825 1829 1833 1837 1841 1845
[16] 1849 1853 1857 1861 1865 1869 1873 1877 1881 1885 1889 1893 1897 1901 1905
[31] 1909 1913 1917 1921 1925 1929 1933 1937 1941 1945 1949 1953 1957 1961 1965
[46] 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 2017 2021

corpus_subset(data_corpus_inaugural, Year > 1945)

Corpus consisting of 19 documents and 4 docvars.
1949-Truman :
"Mr. Vice President, Mr. Chief Justice, and fellow citizens, ..."

1953-Eisenhower :
"My friends, before I begin the expression of those thoughts ..."

1957-Eisenhower :
"The Price of Peace Mr. Chairman, Mr. Vice President, Mr. Chi..."

[ reached max_ndoc ... 16 more documents ]

subset.corpus <- function(x,...) corpus_subset(x,...)

subset(data_corpus_inaugural, Year > 1945)

Corpus consisting of 19 documents and 4 docvars.
1949-Truman :
"Mr. Vice President, Mr. Chief Justice, and fellow citizens, ..."

1953-Eisenhower :
"My friends, before I begin the expression of those thoughts ..."

1957-Eisenhower :
"The Price of Peace Mr. Chairman, Mr. Vice President, Mr. Chi..."

[ reached max_ndoc ... 16 more documents ]

docs_containing <- function(x,pattern,...) x[grep(pattern,x,...)]

c_sub <- docs_containing(data_corpus_inaugural,"[Cc]arnage")
c_sub$President

[1] "Trump"

inaugural_sntc <- corpus_reshape(data_corpus_inaugural,
                                 to="sentences")
inaugural_sntc

Corpus consisting of 5,234 documents and 4 docvars.
1789-Washington.1 :
"Fellow-Citizens of the Senate and of the House of Representa..."

1789-Washington.2 :
"On the one hand, I was summoned by my Country, whose voice I..."

1789-Washington.3 :
"On the other hand, the magnitude and difficulty of the trust..."

[ reached max_ndoc ... 5,231 more documents ]

sntcl <- cbind(docvars(inaugural_sntc),
               len=nchar(inaugural_sntc))
head(sntcl)

                  Year  President FirstName Party len
1789-Washington.1 1789 Washington    George  none 278
1789-Washington.2 1789 Washington    George  none 478
1789-Washington.3 1789 Washington    George  none 436
1789-Washington.4 1789 Washington    George  none 179
1789-Washington.5 1789 Washington    George  none 515
1789-Washington.6 1789 Washington    George  none 654

sntcl.year <- aggregate(len~Year,data=sntcl,mean)
with(sntcl.year,
     scatter.smooth(Year,len,ylab="Average length of sentences in characters"))
/book/data-management-r/09-text-as-data/quanteda-basic/ec8109a52d6bf89e2734838be4f46d8524979854f85cba6b0398eb160dc4dc6c.png 
inaugural_ <- corpus_reshape(data_corpus_inaugural,
                             to="documents")
all(inaugural_$Year == data_corpus_inaugural$Year)

[1] TRUE