close #99 via a new chunk option fig.keep (to filter out undesired plots)

Author: yihui

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: litedown
 Type: Package
 Title: A Lightweight Version of R Markdown
-Version: 0.7.4
+Version: 0.7.5
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666", URL = "https://yihui.org")),
     person("Tim", "Taylor", role = "ctb", comment = c(ORCID = "0000-0002-8587-7113")),

NEWS.md

@@ -1,5 +1,7 @@
 # CHANGES IN litedown VERSION 0.8
 
+- Added a new chunk option `fig.keep` to select plots to be kept in a code chunk (thanks, @Gabrielforest, #99). See https://yihui.org/litedown/#sec:option-fig for documentation.
+
 - The chunk option `results = 'hide'` will imply `collapse = TRUE`, i.e., when text output is hidden, the source blocks will be merged (thanks, @jangorecki, #87). 
 
 - `fuse(text = '# text')` will be treated as Markdown input instead of R code input (thanks, @chuxinyuan, #102).

R/fuse.R

@@ -1097,7 +1097,7 @@ reactor(
   attr.source = NULL, attr.output = NULL, attr.plot = NULL, attr.chunk = NULL,
   attr.message = '.plain .message', attr.warning = '.plain .warning', attr.error = '.plain .error',
   cache = FALSE, cache.path = NULL,
-  dev = NULL, dev.args = NULL, fig.path = NULL, fig.ext = NULL,
+  dev = NULL, dev.args = NULL, fig.path = NULL, fig.ext = NULL, fig.keep = TRUE,
   fig.width = 7, fig.height = 7, fig.dim = NULL, fig.cap = NULL, fig.alt = NULL, fig.env = '.figure',
   tab.cap = NULL, tab.env = '.table', cap.pos = NULL,
   print = NULL, print.args = NULL, time = FALSE,
@@ -1121,15 +1121,15 @@ eng_r = function(x, inline = FALSE, ...) {
     return(fmt_inline(res, x$math))
   }
   args = reactor(
-    'fig.path', 'fig.ext', 'dev', 'dev.args', 'message', 'warning', 'error',
+    'fig.path', 'fig.ext', 'fig.keep', 'dev', 'dev.args', 'message', 'warning', 'error',
     'cache', 'print', 'print.args', 'verbose'
   )
   if (is.character(args$fig.path)) args$fig.path = paste0(args$fig.path, opts$label)
   size = list(width = opts$fig.width, height = opts$fig.height)
   # if fig.dim is provided, override fig.width and fig.height
   if (length(dm <- opts$fig.dim) == 2) size[] = as.list(dm)
   # map chunk options to record() argument names
-  names(args)[1:2] = c('dev.path', 'dev.ext')
+  names(args)[1:3] = c('dev.path', 'dev.ext', 'dev.keep')
   args = dropNULL(args)
   args$dev.args = merge_list(size, opts$dev.args)
   args$cache = list(

docs/02-fuse.Rmd

@@ -777,6 +777,13 @@ Chunk options for plot files include:
     the option `dev.args` (@sec:option-dev), e.g.,
     `dev.args = list(width = 9, height = 7)`.
 
+-   `fig.keep`: Indices of plots to be kept. The indices can be either numeric
+    (positive or negative integers) or logical. Negative integers and false
+    values will remove the corresponding plots. For example, if a code chunk
+    generates 3 plots, `c(1, 3)`, `-2`, and `c(T, F, T)` are equivalent ways for
+    `fig.keep` to remove the second plot. The special value `fig.keep = 'last'`
+    means to keep the last plot only.
+
 -   `fig.path`: A path prefix for plot files. This prefix, joined by the chunk
     label and the plot number, will be the actual plot file path. For example,
     for `fig.path = 'figures/'` and a chunk with the label `foo`, the *i*-th