Knitr plot fragment hook for reveal.js

Plot fragment hook

c0 <- knitr::knit_hooks$get('chunk')

knitr::knit_hooks$set(
  list(
    chunk=function(x,options){
      if(is.null(options$class) & is.null(options$fragIndex)){
        c0(x, options)
      } else if(is.null(options$fragIndex)) {
        classidx <- which(names(options)=="class")
        paste0(
          paste0("<span class='", options$class, "'>"),
          c0(x, options[-classidx]),
          '</span>\n'
        )
      }
      else if(length(options$fragIndex)==1) {
        classidx <- which(names(options)%in%c("class", "fragIndex"))
        str_replace(
          paste0(
            paste0("<span class='", options$class, "' data-fragment-index=", options$fragIndex,">"),
            c0(x, options[-classidx]),
            '</span>\n'
          ),
          "<div class=\"chunk\" id=\"(.*?)\">\\s*<div class=\"rimage default\">(.*)</div>\\s*</div>",
          "\\2"
        )
      } else {
        classidx <- which(names(options)%in%c("class", "fragIndex"))
        str_replace(
          paste0(
            paste0("<span class='", options$class, " fade-in' data-fragment-index=", options$fragIndex[1],">"),
            paste0(
              paste0("<span class='", options$class, " fade-out' data-fragment-index=", options$fragIndex[2],">"),
              c0(x, options[-classidx]),
              '</span>\n'
              ),
            '</span>\n'
            ),
          "<div class=\"chunk\" id=\"(.*?)\">\\s*<div class=\"rimage default\">(.*)</div>\\s*</div>",
          "\\2"
        )
        
      }
        
    }
  )
)