merge columns every other row using Sweave/R/Latex

Question

I am writing a conference abstract booklet using R/Sweave. I have already made the program booklet for printing that contains the id, author, title only.

Now I want to modify it to include the abstract (not for print). But abstracts are lengthy . My thought is to take the cell with the abstract info, and have it display below the row with the author info - expanded across the full width of the page.

ID--author--------title--------------------------------
abstract-----------------------------------------------

So every other row has only one column spanning the width of the entire table. Is there a way to add multicolmn{x} to every other row?

If a solution can't be figured out, advice for how to print full abstracts in a nice way would be welcome. (Something other than "just use landscape" or "adjust column widths")

Also, it doesn't have to be PDF. I could switch to markdown/html - and make it look closer to real conference program schedules that have full abstracts on them. Again, one I figure out how to print a table where every other row has only one column that is the width of the entire table.

If you want to try - Here is a complete MWE for what I have working now. Note that it uses the R package lipsum which has to be installed via devtools/github.

\documentclass{article}

\usepackage{booktabs, multicol, array}
\usepackage[margin=0.75in]{geometry}

%%%%%%%%%%% Let tables to span entire page
\newcolumntype{L}[1]{>{\raggedright\let\newline\\\arraybackslash\hspace{0pt}}m{#1}}

<<echo=FALSE, warning=FALSE, message=FALSE>>=
# devtools::install_github("coolbutuseless/lipsum")
library(lipsum)
library(xtable)
knitr::opts_chunk$set(echo = FALSE, warning=FALSE, message=FALSE)
options(xtable.comment = FALSE)

tblalign <- "lL{0.5cm}|L{4cm}L{6cm}L{8cm}"

# fake data setup
dat <- data.frame(ID = c(1:3), author = substr(lipsum[1:3], 1, 40), 
                  title = substr(lipsum[4:6], 1, 100), 
                  abstract = lipsum[7:9])

names(dat)=c("\\multicolumn{1}{c}{\\textbf{\\large{ID}}}",
             "\\multicolumn{1}{c}{\\textbf{\\large{Author List}}}",
             "\\multicolumn{1}{c}{\\textbf{\\large{Title}}}",
             "\\multicolumn{1}{c}{\\textbf{\\large{Abstract}}}")

@


\begin{document}

<<results='asis'>>=
print(
  xtable(x = dat
         , align = tblalign)

  , table.placement = "H"
  , sanitize.colnames.function=function(x){x}
  , include.rownames = FALSE
  , include.colnames = TRUE
  , size = "small"
  , floating = FALSE
  , hline.after = c(0,1:nrow(dat))
)
@


\end{document}

Answer 1

Split data from abstract manually

out <- dat[,-4]
ab.list <- dat$abstract

then add.to.row

  , add.to.row = list(pos = as.list(1:nrow(out)),
                      command = paste0("\\multicolumn{3}{L{15cm}}{\\textbf{Abstract: }", ab.list, "} \\\\"))

Answer 2

One approach using my package huxtable . I couldn't install lipsum for some reason, so just hacked it. This is in a .Rmd file with output pdf_document .

```{r, results = 'asis'}

lipsum <- rep(do.call(paste, list(rep('blah ', 100), collapse = '')), 10)
dat <- data.frame(ID = c(1:3), author = substr(lipsum[1:3], 1, 40), 
              title = substr(lipsum[4:6], 1, 100), 
              abstract = lipsum[7:9], stringsAsFactors = FALSE)

library(huxtable)

# shape data
datmat <- matrix(NA_character_, nrow(dat) * 2, 3)
datmat[seq(1, nrow(datmat), 2), ] <- as.matrix(dat[, c('ID', 'author', 'title')])
datmat[seq(2, nrow(datmat), 2), 1] <- dat$abstract

# print as PDF
ht <- as_huxtable(datmat)
colspan(ht)[seq(2, nrow(ht), 2), 1] <- 3
wrap(ht) <- TRUE
col_width(ht) <- c(.2, .2, .6)
number_format(ht) <- 0
ht
```