Turning a pdf book into machine readable format

A few days ago a well known Sociologist, Erik Olin Wright, died from Leukemia. Torkild Lyngstand then posted on twitter his ‘intellectual biography’ which is an interesting document that outlines how he ended up being a Marxist. This document is a pdf book that has two actual book pages per pdf page.

Although this is perfectly fine for reading on a computer, I usually don’t like to read anything longer than 15 pages on my computer. So I decided I would turn this book into machine readable text with R for my Kindle.

Spoiler: I couldn’t do it, so help me out!

Firs things first. I will use the magick and tabulizer packages. tabulizer has a dependency with rJava which is a bit difficult to handle. I wrote this blogpost explaining how to install rJava on Windows 10 and it’s helped me inmensely not to waste time in the installation process.

After installing both packages successfully, I loaded them, and split the pdf into separate pages using tabulizer::split_pdf.

library(magick)
Sys.setenv(JAVA_HOME="C:/Program Files/Java/jdk-11.0.2/")
library(tabulizer)

url <- "https://www.ssc.wisc.edu/~wright/Published%20writing/FallingIntoMarxismChoosingToStay.pdf"
all_pages <- tabulizer::split_pdf(url)

all_pages

##  [1] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce401.pdf"
##  [2] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce402.pdf"
##  [3] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce403.pdf"
##  [4] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce404.pdf"
##  [5] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce405.pdf"
##  [6] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce406.pdf"
##  [7] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce407.pdf"
##  [8] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce408.pdf"
##  [9] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce409.pdf"
## [10] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce410.pdf"
## [11] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce411.pdf"
## [12] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce412.pdf"
## [13] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce413.pdf"
## [14] "C:\\Users\\Cimentadaj\\AppData\\Local\\Temp\\RtmpYnb7KJ\\file1ba438de3ce414.pdf"

tabulizer::split_df saved each page on a separate pdf in a temporary directory. Now we only have to develop a function to clean one page and apply it to all middle pages (that is, excluding the first and last because they have a slightly different format).

After hard work, I developed the function convert_page which accepts one pdf page crops all the corners so that only text is available.

convert_page <- function(page) {
  page <- magick::image_read_pdf(page)
  separator <- image_info(page)$width / 2
  first_page <- image_crop(page, geometry_area(width = separator))
  second_page <- image_crop(page, geometry_area(x_off = separator, y_off = 1))
  
  size <- geometry_area(width = 1400,
                        height = 2200,
                        x_off = 300,
                        y_off = 200)
  
  first_page <- image_crop(first_page, size)
  
  
  size <- geometry_area(width = 1400,
                        height = 2200,
                        x_off = 130,
                        y_off = 200)
  
  second_page <- image_crop(second_page, size)
  
  f_text <- image_ocr(first_page)
  s_text <- image_ocr(second_page)
  
  complete_page <- paste0(f_text, s_text)
  
  complete_page
}

Let’s look at an actual example. Below is a picture of page 4:

page_four <- magick::image_read_pdf(all_pages[4])
image_resize(page_four, geometry_size_percent(width = 40))

convert_page crops the sides to obtain the leftmost page:

separator <- image_info(page_four)$width / 2
first_page <- image_crop(page_four, geometry_area(width = separator))
second_page <- image_crop(page_four, geometry_area(x_off = separator, y_off = 1))

size <- geometry_area(width = 1400,
                      height = 2200,
                      x_off = 300,
                      y_off = 200)

first_page <- image_crop(first_page, size)


size <- geometry_area(width = 1400,
                      height = 2200,
                      x_off = 130,
                      y_off = 200)

second_page <- image_crop(second_page, size)

image_resize(first_page, geometry_size_percent(width = 40))

And for the rightmost page:

image_resize(second_page, geometry_size_percent(width = 40))

Finally, it converts and merges both pages into text with:

f_text <- image_ocr(first_page)
s_text <- image_ocr(second_page)

complete_page <- paste0(f_text, s_text)

cat(complete_page)

## thusiastic and involved in their children’s school projects and intellectual pur-
## suits. My mother would carefully go over term papers with each of us, giving us
## both editorial advice and substantive suggestions. We were members of the Law-
## rence Unitarian Fellowship, which was made up of, to a substantial extent, uni-
## versity families. Sunday morning services were basically interdisciplinary semi-
## nars on matters of philosophical and social concern; Sunday school was an
## extended curriculum on world religions. | knew by about age ten that | wanted
## to be a professor. Both of my parents were academics. Both of my siblings be-
## came academics. Both of their spouses are academics. (Only my wife, a clinical
## psychologist, is not an academic, although her father was a professor.) ‘The only
## social mobility in my family was interdepartmental. It just felt natural to go into
## the family business.
## 
## Lawrence was a delightful, easy place to grow up. Although Kansas was a po-
## litically conservative state, Lawrence was a vibrant, liberal community. My ear-
## liest form of political activism centered on religion: | was an active member of a
## Unitarian youth group called Liberal Religious Youth, and in high school { went
## out of my way to argue with Bible Belt Christians about their belief in God. The
## early 1960s also witnessed my earliest engagement with social activism. The civil
## rights movement came to Lawrence first in the form of an organized boycott of
## a local segregated swimming pool in the 1950s and then in the form of civil rights
## rallies in the 1960s. In 1963 I went to the Civil Rights March on Washington and
## heard Martin Luther King Jr’s “I have a dream” speech. My earliest sense of pol-
## itics was that at its core it was about moral questions of social justice, not prob-
## lems of economic power and interests.
## 
## My family, also, was liberal, supporting the civil rights movement and other
## liberal causes; but while the family culture encouraged an intellectual interest in
## social and moral concerns, it was not intensely political. We would often talk
## about values, and the Unitarian Fellowship we attended also stressed humanis-
## tic, socially concerned values, but these were mostly framed as matters of indi-
## vidual responsibility and morality not as the grounding of a coherent political
## challenge to social injustice. My only real exposure toa more radical political per-
## spective came through my maternal grandparents, Russian Jewish immigrants
## who had come to the United States before World War I and lived near us in Law-
## rence, and my mother’s sister’s family in New York. Although I was not aware of
## this at the time, my grandparents and the New York relatives were Communists.
## This was never openly talked about, but from time to time I would hear glowing
## things said about the Soviet Union, socialism would be held out as an ideal, and
## America and capitalism would be criticized in emotionally laden ways. My cous-
## ins in New York were especially vocal about this, and in the mid-1g60s when I be-
## came more engaged in political matters, intense political discussions with my
## New York relatives contributed significantly to anchoring my radical sensibilities.
## 
## My interest in social sciences began in earnest in high school. fn Lawrence it
## was easy for academically oriented kids to take courses at the University of Kan-
## sas, and in my senior year | took a political science course on American politics.
## For my term project | decided to do a survey of children’s attitudes toward the
## American presidency and got permission to administer a questionnaire to several
## hundred students from grades 1-12 in the public schools. | then organized a party
## with my friends to code the data and produce graphs of how various attitudes
## changed by age. I'he most striking finding was that, in response to the question,
## “Would you like to be President of the United States when you grow up?” there
## were more girls who said yes than boys through third grade, after which the rate
## for girls declined dramatically.
## 
## By the time I graduated from high school in 1964, I had enough university
## credits and advanced placement credits to enter KU as a second-semester soph-
## omore, and that is what | had planned to do. Nearly all of my friends were going
## to KU. It just seemed like the thing to do. A friend of my parents, Karl Heider,
## gave me, as a Christmas present in my senior year in high school, an application
## form to Harvard. He was a graduate student at Harvard in anthropology at the
## time. I filled it out and sent it in. Harvard was the only place to which I applied,
## not out of inflated self-confidence but because it was the only application I got as
## a Christmas present. When | eventually was accepted (initially I was on the wait-
## ing list), the choice was thus between KU and Harvard. I suppose this was a
## “choice” since I could have decided to stay at KU. However, it just seemed so ob-
## vious; there was no angst, no weighing of alternatives, no thinking about the pros
## and cons. Thus, going to Harvard in a way just happened.
## 
## Like many students who began university in the mid-1960s, my political ideas
## were rapidly radicalized as the Viet Nam War escalated and began to impinge on
## our lives. I was not a student leader in activist politics, but I did actively partici-
## pate in demonstrations, rallies, fasts for peace, and endless political debate. At
## Harvard I majored in social studies, an intense interdisciplinary social science
## major centering on the classics of social theory, and in that program I was first ex-
## posed to the more abstract theoretical issues that bore on the political concerns
## of the day: the dynamics of capitalism, the nature of power and domination, the
## importance of elites in shaping American foreign policy, and the problem of

If we pass the pdf page directly to convert_page, it will do it all in one take:

cat(convert_page(all_pages[4]))

## thusiastic and involved in their children’s school projects and intellectual pur-
## suits. My mother would carefully go over term papers with each of us, giving us
## both editorial advice and substantive suggestions. We were members of the Law-
## rence Unitarian Fellowship, which was made up of, to a substantial extent, uni-
## versity families. Sunday morning services were basically interdisciplinary semi-
## nars on matters of philosophical and social concern; Sunday school was an
## extended curriculum on world religions. | knew by about age ten that | wanted
## to be a professor. Both of my parents were academics. Both of my siblings be-
## came academics. Both of their spouses are academics. (Only my wife, a clinical
## psychologist, is not an academic, although her father was a professor.) ‘The only
## social mobility in my family was interdepartmental. It just felt natural to go into
## the family business.
## 
## Lawrence was a delightful, easy place to grow up. Although Kansas was a po-
## litically conservative state, Lawrence was a vibrant, liberal community. My ear-
## liest form of political activism centered on religion: | was an active member of a
## Unitarian youth group called Liberal Religious Youth, and in high school { went
## out of my way to argue with Bible Belt Christians about their belief in God. The
## early 1960s also witnessed my earliest engagement with social activism. The civil
## rights movement came to Lawrence first in the form of an organized boycott of
## a local segregated swimming pool in the 1950s and then in the form of civil rights
## rallies in the 1960s. In 1963 I went to the Civil Rights March on Washington and
## heard Martin Luther King Jr’s “I have a dream” speech. My earliest sense of pol-
## itics was that at its core it was about moral questions of social justice, not prob-
## lems of economic power and interests.
## 
## My family, also, was liberal, supporting the civil rights movement and other
## liberal causes; but while the family culture encouraged an intellectual interest in
## social and moral concerns, it was not intensely political. We would often talk
## about values, and the Unitarian Fellowship we attended also stressed humanis-
## tic, socially concerned values, but these were mostly framed as matters of indi-
## vidual responsibility and morality not as the grounding of a coherent political
## challenge to social injustice. My only real exposure toa more radical political per-
## spective came through my maternal grandparents, Russian Jewish immigrants
## who had come to the United States before World War I and lived near us in Law-
## rence, and my mother’s sister’s family in New York. Although I was not aware of
## this at the time, my grandparents and the New York relatives were Communists.
## This was never openly talked about, but from time to time I would hear glowing
## things said about the Soviet Union, socialism would be held out as an ideal, and
## America and capitalism would be criticized in emotionally laden ways. My cous-
## ins in New York were especially vocal about this, and in the mid-1g60s when I be-
## came more engaged in political matters, intense political discussions with my
## New York relatives contributed significantly to anchoring my radical sensibilities.
## 
## My interest in social sciences began in earnest in high school. fn Lawrence it
## was easy for academically oriented kids to take courses at the University of Kan-
## sas, and in my senior year | took a political science course on American politics.
## For my term project | decided to do a survey of children’s attitudes toward the
## American presidency and got permission to administer a questionnaire to several
## hundred students from grades 1-12 in the public schools. | then organized a party
## with my friends to code the data and produce graphs of how various attitudes
## changed by age. I'he most striking finding was that, in response to the question,
## “Would you like to be President of the United States when you grow up?” there
## were more girls who said yes than boys through third grade, after which the rate
## for girls declined dramatically.
## 
## By the time I graduated from high school in 1964, I had enough university
## credits and advanced placement credits to enter KU as a second-semester soph-
## omore, and that is what | had planned to do. Nearly all of my friends were going
## to KU. It just seemed like the thing to do. A friend of my parents, Karl Heider,
## gave me, as a Christmas present in my senior year in high school, an application
## form to Harvard. He was a graduate student at Harvard in anthropology at the
## time. I filled it out and sent it in. Harvard was the only place to which I applied,
## not out of inflated self-confidence but because it was the only application I got as
## a Christmas present. When | eventually was accepted (initially I was on the wait-
## ing list), the choice was thus between KU and Harvard. I suppose this was a
## “choice” since I could have decided to stay at KU. However, it just seemed so ob-
## vious; there was no angst, no weighing of alternatives, no thinking about the pros
## and cons. Thus, going to Harvard in a way just happened.
## 
## Like many students who began university in the mid-1960s, my political ideas
## were rapidly radicalized as the Viet Nam War escalated and began to impinge on
## our lives. I was not a student leader in activist politics, but I did actively partici-
## pate in demonstrations, rallies, fasts for peace, and endless political debate. At
## Harvard I majored in social studies, an intense interdisciplinary social science
## major centering on the classics of social theory, and in that program I was first ex-
## posed to the more abstract theoretical issues that bore on the political concerns
## of the day: the dynamics of capitalism, the nature of power and domination, the
## importance of elites in shaping American foreign policy, and the problem of

We pass all middle pages to convert_page to convert them to text:

middle_pages <- lapply(all_pages[3:(length(all_pages) - 1)], convert_page)
cat(middle_pages[[1]])

## versity of Western Australia); music camp (1 played viola); assisting in a lab. And
## in college, it was much the same: volunteering as a photographer on an archae-
## ological dig in Hawaii; teaching in a high school enrichment program for mi-
## nority kids; traveling in urope. The closest thing to an ordinary paying job |
## ever had was occasionally selling hot dogs at football games in my freshman year
## in college. What is more, the ivory towers that [ have inhabited since the mid-
## 1960s have been located in beautiful physical settings, filled with congenial and
## interesting colleagues and students, and animated by exciting ideas. This, then,
## is the first fundamental fact of my life as an academic: [ have been extraordinar-
## ily lucky and have always lived what can only be considered a life of extreme priv-
## ilege. Nearly all of the time [ am doing what [ want to do; what I do gives me a
## sense of fulfillment and purpose; and | am paid well for doing it.
## 
## Here is the second fundamental fact of my academic life: since the early
## 19708, my intellectual life has been firmly anchored in the Marxist tradition. The
## core of my teaching as a professor has centered on communicating the central
## ideas and debates of contemporary Marxism and allied traditions of emancipa-
## tory social theory. The courses I have taught have had names like Class, State and
## Ideology: An Introduction to Marxist Sociology; Envisioning Real Utopias; Mars-
## ist Theories of the State; Alternative Foundations of Class Analysis. My energies
## in institution building have all involved creating and expanding arenas within
## which radical system-challenging ideas could flourish: creating a graduate pro-
## gram in class analysis and historical change in the Sociology Department at the
## University of Wisconsin—Madison; establishing the A. E. Havens Center, a re-
## search institute for critical scholarship at Wisconsin; organizing an annual con-
## ference for activists and academics, now called RadFest, which has been held
## every year since 1983. And my scholarship has been primarily devoted to recon-
## structing Marxism as a theoretical framework and research tradition. While the
## substantive preoccupations of this scholarship have shifted over the past thirty
## years, its central mission has not.
## 
## As in any biography, this pair of facts is the result of a trajectory of circum-
## stances and choices: circumstances that formed me and shaped the range of
## choices I encountered, and choices that in turn shaped my future circumstances.
## Some of these choices were made easily, with relatively little weighing of alter-
## natives, sometimes even without much awareness that a choice was actually be-
## ing made; others were the result of protracted reflection and conscious decision
## making, sometimes with the explicit understanding that the choice being made
## would constrain possible choices in the future. Six such junctures of circum-
## stance and choice seem especially important to me in shaping the contours of
## my academic career. ‘The first was posed incrementally in the early 1970s: the
## choice to identify my work primarily as contributing to Marxism rather than
## simply using Marxism. The second concerns the choice, made just before grad-
## uate school at the University of California, Berkeley, to be a sociologist, rather
## than some other ist. ‘The third was the choice to become what some people de-
## scribe as multivariate Marxist: to be a Marxist sociologist who engages in grandi-
## ose, perhaps overblown, quantitative research, The fourth choice was the choice
## of which academic department to be in. This choice was acutely posed to me
## in 1987 when I spent a year as a visiting professor at the University of Califor-
## nia, Berkeley. | had been offered a position there, and | had to decide whether
## I wanted to return to Wisconsin. Returning to Madison was unquestionably a
## choice that shaped subsequent contexts of choice. The fifth choice has been
## posed and reposed to me with increasing intensity since the late 1980s: the
## choice to stay a Marxist in this world of post-Marxisms when many of my intel-
## lectual comrades have decided for various good, and sometimes perhaps not so
## good, reasons to recast their intellectual agenda as being perhaps friendly to, but
## outside of, the Marxist tradition. Finally, the sixth important choice was to shift
## my central academic work from the study of class structure to the problem of en-
## visioning real utopias.
## 
## To set the stage for this reflection on choice and constraint, I need to give a
## brief account of the circumstances of my life that brought me into the arena of
## these choices.
## 
## Growing Up
## 
## I was born in Berkeley, California, in 1947 while my father, who had received a
## PhD in psychology before World War II, was in medical school on the GI Bill.
## When he finished his medical training in 1951, we moved to Lawrence, Kansas,
## where he became the head of the program in clinical psychology at Kansas Uni-
## versity (KU) and a professor of psychiatry in the KU Medical School. Because of
## antinepotism rules at the time, my mother, who also had a PhD in psychology,
## was not allowed to be employed at the university, so throughout the 1950s she did
## research on various research grants. In 1961, when the state law on such things
## changed, she became a professor of rehabilitation psychology.
## 
## Life in my family was intensely intellectual. Dinner table conversation would
## often revolve around intellectual matters, and my parents were always deeply en-

Ok, everything’s looking good. Because the first and last pages have different croping dimensions, I slightly adapt the geometry_area to do it manually:

### First page
first_page <- magick::image_read_pdf(all_pages[2])
image_resize(first_page, geometry_size_percent(width = 40))

separator <- image_info(first_page)$width / 2

size <- geometry_area(width = 1400,
                      height = 1700,
                      x_off = separator + 100,
                      y_off = 650)

first_page <- image_crop(first_page, size)
image_resize(first_page, geometry_size_percent(width = 40))

first_page <- image_ocr(first_page)
###


### Last page
last_page <- magick::image_read_pdf(all_pages[14])
image_resize(last_page, geometry_size_percent(width = 40))

separator <- image_info(last_page)$width / 2

size <- geometry_area(width = separator - 400,
                      height = 500,
                      x_off = 150,
                      y_off = 260)

last_page <- image_crop(last_page, size)
image_resize(last_page, geometry_size_percent(width = 70))

last_page <- image_ocr(last_page)
###

Ok, the hard work is over! Now we need to merge all of the pages together and print a subset of the text:

final_document <- paste0(first_page, Reduce(paste0, middle_pages), last_page)
cat(paste0(substring(final_document, 0, 5000), "..."))

## Falling into Marxism; Choosing to Stay
## 
## Erik Olin Wright received his PhD from the University of California, Berkeley, and
## has taught at the University of Wisconsin since then. His academic work has been
## centrally concerned with reconstructing the Marxist tradition of social theory and
## research in ways that attempt to make it more relevant to contemporary concerns
## and more cogent as a scientific framework of analysis. His empirical research has
## focused especially on the changing character of class relations in developed capi-
## talist societies. Since 1992 he has directed the Real Utopias Project, which explores
## a range of proposals for new institutional designs that embody emancipatory ideals
## and yet are attentive to issues of pragmatic feasibility. His principle publications
## include The Politics of Punishment: A Critical Analysis of Prisons in America;
## Class, Crisis and the State; Classes; Reconstructing Marxism (with Elliott Sober
## and Andrew Levine); Interrogating Inequality; Class Counts: Comparative Stud-
## ies in Class Analysis; and Deepening Democracy: Innovations in Empowered
## Participatory Governance (with Archon Fung). He is married to Marcia Kahn
## Wright, a clinical psychologist working in community mental health, and has tvo
## grown daughters, Jennifer and Rebecca.
## 
## [ have been in school continuously for more than fifty vears: since I entered
## kindergarten in 1952, there has never been a September when I wasn’t beginning
## a school year. | have never held a nine-to-five job with fixed hours and a boss
## telling me what to do. In high school, my summers were always spent in vari-
## ous kinds of interesting and engaging activities — traveling home from Australia
## where my family spent a year (my parents were Fulbright professors at the Uni-
## versity of Western Australia); music camp (1 played viola); assisting in a lab. And
## in college, it was much the same: volunteering as a photographer on an archae-
## ological dig in Hawaii; teaching in a high school enrichment program for mi-
## nority kids; traveling in urope. The closest thing to an ordinary paying job |
## ever had was occasionally selling hot dogs at football games in my freshman year
## in college. What is more, the ivory towers that [ have inhabited since the mid-
## 1960s have been located in beautiful physical settings, filled with congenial and
## interesting colleagues and students, and animated by exciting ideas. This, then,
## is the first fundamental fact of my life as an academic: [ have been extraordinar-
## ily lucky and have always lived what can only be considered a life of extreme priv-
## ilege. Nearly all of the time [ am doing what [ want to do; what I do gives me a
## sense of fulfillment and purpose; and | am paid well for doing it.
## 
## Here is the second fundamental fact of my academic life: since the early
## 19708, my intellectual life has been firmly anchored in the Marxist tradition. The
## core of my teaching as a professor has centered on communicating the central
## ideas and debates of contemporary Marxism and allied traditions of emancipa-
## tory social theory. The courses I have taught have had names like Class, State and
## Ideology: An Introduction to Marxist Sociology; Envisioning Real Utopias; Mars-
## ist Theories of the State; Alternative Foundations of Class Analysis. My energies
## in institution building have all involved creating and expanding arenas within
## which radical system-challenging ideas could flourish: creating a graduate pro-
## gram in class analysis and historical change in the Sociology Department at the
## University of Wisconsin—Madison; establishing the A. E. Havens Center, a re-
## search institute for critical scholarship at Wisconsin; organizing an annual con-
## ference for activists and academics, now called RadFest, which has been held
## every year since 1983. And my scholarship has been primarily devoted to recon-
## structing Marxism as a theoretical framework and research tradition. While the
## substantive preoccupations of this scholarship have shifted over the past thirty
## years, its central mission has not.
## 
## As in any biography, this pair of facts is the result of a trajectory of circum-
## stances and choices: circumstances that formed me and shaped the range of
## choices I encountered, and choices that in turn shaped my future circumstances.
## Some of these choices were made easily, with relatively little weighing of alter-
## natives, sometimes even without much awareness that a choice was actually be-
## ing made; others were the result of protracted reflection and conscious decision
## making, sometimes with the explicit understanding that the choice being made
## would constrain possible choices in the future. Six such junctures of circum-
## stance and choice seem especially important to me in shaping the contours of
## my academic career. ‘The first was posed incrementally in the early 1970s: the
## choice to identify my work primarily as contributing to Marxism rather than
## simply using Marxism. The second concerns the choice, made just before grad-
## uate school at the University ...

There we go, nicely formatted text all obtained from pdf images (after carefully revising the text there are many mistakes, but this was a lightning post, so no time to tidy up the text).

rmd_path <- tempfile(pattern = 'our_book', fileext = ".Rmd")

rmd_preamble <-"---
  title: 'Final Book'
  output: html_document
---\n\n"

final_document <- paste0(rmd_preamble, final_document)
  
writeLines(final_document, con = rmd_path, useBytes = TRUE)

# Bookdown compiles all .Rmd in the working directory, so we move
# to the temporary directory where the book is
setwd(dirname(rmd_path))
bookdown::render_book(rmd_path, bookdown::epub_book())

txt_path <- tempfile(pattern = 'our_book', fileext = ".txt")

writeLines(final_document, con = txt_path, useBytes = TRUE)

# First download Calibre
path <- paste0(Sys.getenv("PATH"), ";", "C:\\Program Files\\Calibre2")
Sys.setenv(PATH = path)
bookdown::calibre(txt_path, paste0(dirname(txt_path), "/erik_wright.mobi"))