Pandoc document conversion failed when trying to add selectInput() to flexdashboard

Im trying to add a simple selectInput() to my flexdashboard but I get:

File shared/selectize/css/selectize.bootstrap3.css not found in resource path
Error: pandoc document conversion failed with error 99
Execution halted

---
title: "My Dashboard"
output: flexdashboard::flex_dashboard
---
  
### Chart 1

```{r}
library(readr)
library(haven)
library(shiny)

subs<-structure(list(Sold_Pr = c(6500, 173000, 60000, 73000, 155000, 
105000, 140000, 39900, 73500, 46000, 99900, 180000, 164000, 120000, 
206000, 160000, 67400, 215000, 145000, 175000, 350000, 425000, 
435000, 490000, 545000, 585000), Area = structure(c(1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("411", "415", "981", 
"8001", "8002", "8003", "8004", "8005", "8006", "8007", "8008", 
"8009", "8010", "8011", "8012", "8013", "8014", "8015", "8016", 
"8017", "8018", "8019", "8020", "8021", "8022", "8023", "8024", 
"8025", "8026", "8027", "8028", "8029", "8030", "8031", "8034", 
"8035", "8037", "8038", "8039", "8040", "8041", "8042", "8043", 
"8044", "8045", "8046", "8047", "8048", "8049", "8050", "8051", 
"8052", "8053", "8055", "8056", "8057", "8058", "8059", "8060", 
"8061", "8062", "8063", "8064", "8065", "8066", "8067", "8068", 
"8069", "8070", "8071", "8072", "8073", "8074", "8075", "8076", 
"8077"), class = "factor"), Closed_Date = structure(c(18668, 
18933, 18716, 18740, 18639, 18845, 18708, 18676, 18733, 18695, 
18715, 18709, 18794, 18803, 18750, 18787, 18906, 18810, 18855, 
18870, 18626, 18786, 18808, 18864, 18961, 18914), class = "Date")), row.names = c(NA, 
-26L), class = c("tbl_df", "tbl", "data.frame"))

selectInput("ar", label = "Select Area:",
            choices =unique(subs$Area), selected = unique(subs$Area)[1])

```

Solution

Not sure what's the reason for this issue. Probably related to ongoing efforts to support more recent versions of Bootstrap. Anyway you could make you code work by specifying the bootstrap version you want to use in the YAML like so (also see this vignette):

Note: I also had to specify the bootswatch theme to get the default flexdashboard look.

---
title: "My Dashboard"
output: 
  flexdashboard::flex_dashboard:
    theme:
      version: 3
      bootswatch: cosmo
---
  
### Chart 1

```{r}
library(readr)
library(haven)
library(shiny)

subs <- structure(list(Sold_Pr = c(
  6500, 173000, 60000, 73000, 155000,
  105000, 140000, 39900, 73500, 46000, 99900, 180000, 164000, 120000,
  206000, 160000, 67400, 215000, 145000, 175000, 350000, 425000,
  435000, 490000, 545000, 585000
), Area = structure(c(
  1L, 1L, 1L,
  1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
  1L, 2L, 2L, 2L, 2L, 2L, 2L
), .Label = c(
  "411", "415", "981",
  "8001", "8002", "8003", "8004", "8005", "8006", "8007", "8008",
  "8009", "8010", "8011", "8012", "8013", "8014", "8015", "8016",
  "8017", "8018", "8019", "8020", "8021", "8022", "8023", "8024",
  "8025", "8026", "8027", "8028", "8029", "8030", "8031", "8034",
  "8035", "8037", "8038", "8039", "8040", "8041", "8042", "8043",
  "8044", "8045", "8046", "8047", "8048", "8049", "8050", "8051",
  "8052", "8053", "8055", "8056", "8057", "8058", "8059", "8060",
  "8061", "8062", "8063", "8064", "8065", "8066", "8067", "8068",
  "8069", "8070", "8071", "8072", "8073", "8074", "8075", "8076",
  "8077"
), class = "factor"), Closed_Date = structure(c(
  18668,
  18933, 18716, 18740, 18639, 18845, 18708, 18676, 18733, 18695,
  18715, 18709, 18794, 18803, 18750, 18787, 18906, 18810, 18855,
  18870, 18626, 18786, 18808, 18864, 18961, 18914
), class = "Date")), row.names = c(
  NA,
  -26L
), class = c("tbl_df", "tbl", "data.frame"))
```                                                          
                                                                  
```{r, eval=TRUE}
selectInput("ar",
  label = "Select Area:",
  choices = unique(subs$Area), selected = unique(subs$Area)[1]
)
```