CODEWITHSUNDEEP
rdplyrr-packagerlangtidyeval
Kuba_
Kuba_

Reputation: 814

Using tidy eval in R packages

I have a function stacked_plot() that uses tidy evaluation to make a stacked plot. I wanted to include it in my package and make the other function from that package to call it. Here's the minimal example:

stacked_plot <- function(data, what, by = NULL, date_col = date){

  by <- rlang::enquo(by)
  what <- rlang::ensym(what)
  date_col <- rlang::ensym(date_col)
  data <- data %>%
    dplyr::group_by(!!date_col, !!by) %>%
    dplyr::summarise(!!what := sum(!!what, na.rm = TRUE)) %>%
    dplyr::ungroup() %>%
    tidyr::complete(!!date_col, !!by, fill = rlang::list2(!!what := 0))

  p <- data %>%
    ggplot2::ggplot(ggplot2::aes(!!date_col, !!what, fill = !!by)) +
    ggplot2::geom_area(position = 'stack')
  print(p)
}

#' @importFrom rlang .data
call_plot <- function() {
  to_plot <- data.frame(date = rep(seq(lubridate::ymd('2020-01-01'),
                                       lubridate::ymd('2020-03-30'),
                                       by = '1 day'), each = 3)) %>%
    dplyr::mutate(cat = rep(c('A', 'B', 'C'), 90), v1 = runif(270))

  p <- to_plot %>%
    stacked_plot(what = .data$v1, by = .data$cat)
  return(p)
}

Incorporating stacked_plot() into a package worked fine and I can call it interactively. However, the call_plot() after load_all() results in an error. Here's the rlang::last_error() output:

rlang::last_error()
<error/rlang_error>
Only strings can be converted to symbols
Backtrace:
  1. global::call_plot()
 10. mmmtools::stacked_plot(., what = .data$v1, by = .data$cat)
 11. rlang::ensym(what) R/stacked_plot.R:4:2
Run `rlang::last_trace()` to see the full context.

I believe this is due to some idiosyncracy of tidy evaluation. However I can't really find any source about pecularities of using tidyeval in R packages. The only thing I know is that I can't really use quoted variables directly and use .data$variable pattern instead, which I did in call_plot().

How can I use adjust stacked_plot() to make it usable from other package functions?

Upvotes: 4

Views: 413

Answers (1)

akrun
akrun

Reputation: 887781

It seems that the OP wanted to take unquoted column names. If that is the case, change the ensym to enquo

stacked_plot <- function(data, what, by = NULL, date_col = date){

  by <- rlang::enquo(by)
  what <- rlang::enquo(what)
  date_col <- rlang::enquo(date_col)
  data %>%
    dplyr::group_by(!! date_col, !!by) %>%
    dplyr::summarise(!!what := sum(!!what, na.rm = TRUE)) %>%
      dplyr::ungroup() %>%
      tidyr::complete(!!date_col, !!by, fill = rlang::list2(!!what := 0)) %>%  
    ggplot2::ggplot(ggplot2::aes(!!date_col, !!what, fill = !!by)) +
     ggplot2::geom_area(position = 'stack')



}

call_plot <- function() {
  to_plot <- data.frame(date = rep(seq(lubridate::ymd('2020-01-01'),
                                       lubridate::ymd('2020-03-30'),
                                       by = '1 day'), each = 3)) %>%
    dplyr::mutate(cat = rep(c('A', 'B', 'C'), 90), v1 = runif(270))

  p <- to_plot %>%
    stacked_plot(what =  v1, by =  cat)
  return(p)
}

-call the function

call_plot()

enter image description here

In addition, the enquo + !! can be totally replaced with {{}}

stacked_plot <- function(data, what, by = NULL, date_col = date){



  data %>%
    dplyr::group_by({{date_col}}, {{by}}) %>%
    dplyr::summarise( {{what}} := sum({{what}}, na.rm = TRUE)) %>%
    dplyr::ungroup() %>%
    tidyr::complete({{date_col}}, {{by}}, fill = rlang::list2({{what}} := 0))  %>% 
    ggplot2::ggplot(ggplot2::aes({{date_col}}, {{what}}, fill = {{by}})) +
    ggplot2::geom_area(position = 'stack')



}

and it can be as in the previous one

call_plot()

Upvotes: 5

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