Use dataframe attr within 2 function lapply

Question

I wrote a function to create a div using the name of each column in a data frame. I want the text of the div to be the data frame's "labels" attr

library(shiny)

df <- data.frame(x = c(1, 2, 3), y = c(4, 5, 6), z = c(7, 8, 9))
attr(df$x, "labels") <- "a"
attr(df$y, "labels") <- "b"
attr(df$z, "labels") <- "c"

rowBlocks <- function(data, name, label)
{
  div(
    drag = name,
    div(class = "active-title", id = name, label))
}

lapply(sort(colnames(df[,1:3])), rowBlocks, 
       #Rather than have "Text below, 
       # How do I get the df attr "label" on hover?
                 data = df, label = "Text")

I wasn't sure how to phrase this question but I think I need to use an lapply with two functions, and I'm also struggling to access the attr within an lapply.

Desired Output

[[1]]
<div drag="x">
  <div class="active-title" id="x">a</div>
</div>

[[2]]
<div drag="y">
  <div class="active-title" id="y">b</div>
</div>

[[3]]
<div drag="z">
  <div class="active-title" id="z">c</div>
</div>

I tried using label = attr(df$name, "label") but it interprets name literally, not using the actual name variable... Any help appreciated!

Answer 1

You can either change your rowBlocks function to look up the labels for you from the data

rowBlocks <- function(data, name){
  div(
    drag = name,
    div(class = "active-title", id = name, attr(data[[name]],"labels")))
}

lapply(sort(colnames(df[,1:3])), rowBlocks, 
       data = df)

or you could change how you are calling it to iterate over the names and labels

rowBlocks <- function(name, label){
  div(
    drag = name,
    div(class = "active-title", id = name, label))
}
cols <- sort(colnames(df[,1:3]))
Map(rowBlocks, cols, sapply(cols, function(x) attr(df[[x]], "labels")))

Here we use Map rather than lapply because we need to loop over multiple inputs.