R Shiny. No applicable method for 'mutate' applied to an object of class "c('reactiveExpr', 'reactive', 'function')"

Question

I am trying to create a very simple Shiny app that could let a user select a set of tables and see which variables are shared by those tables.

My input data (named "df" in my code below) looks like this:

Tables	Variables
tabla_1	A
tabla_1	Z
tabla_1	Y
tabla_1	V
tabla_1	B
tabla_2	H
tabla_2	B
tabla_2	A
tabla_2	U
tabla_3	U
tabla_3	S
tabla_3	M
tabla_4	U
tabla_4	A
tabla_4	B
tabla_4	V
tabla_4	Q
tabla_4	O
tabla_4	F

If the user selected all the tables available to compare them, the output would have to look like this (mytable1 in my code below):

Variables	tabla_1	tabla_2	tabla_3	tabla_4
A	Yes	Yes	No	Yes
Z	Yes	No	No	No
Y	Yes	No	No	No
V	Yes	No	No	Yes
B	No	Yes	No	Yes
H	No	Yes	No	No
U	No	Yes	Yes	Yes
S	No	Yes	Yes	No
M	No	No	Yes	No
Q	No	No	No	Yes
O	No	No	No	Yes
F	No	No	No	Yes

Right now my code looks like this:

library(shiny)
library(dplyr)



ui <- fluidPage(
  title = "Compare Data Tables",
  
    sidebarPanel(
        
        checkboxGroupInput("show_tables", "Tables to compare",
                           unique(df$Tables), selected = unique(df$Tables)
                           
                           ),
        
        mainPanel("comparison", DT::dataTableOutput("mytable1"))))

server <- function(input, output) {
  
  
  
  filter1 <- reactive({subset(df, Tables == input$show_tables)})
  
  result<-filter1 %>% 
           mutate(n = "Yes")%>%
           pivot_wider(names_from = Tables, values_from = n, values_fill = list(n = "No"))
  
  output$mytable1 <- DT::renderDataTable({
    DT::datatable(result)
  })
  
}

shinyApp(ui, server)

After I run that I get this message:

Error in UseMethod("mutate") : no applicable method for 'mutate' applied to an object of class "c('reactiveExpr', 'reactive', 'function')"

I am not sure what might be wrong. Is it that I cannot use the mutate function to a reactive object. If so, what could I use instead to get the same output?

Thanks a lot for any suggestions.

user_3732271 · Answer

We could change the server part to

server <- function(input, output) {
  
  
  
  result <- reactive({
    
    req(input$show_tables)
    tmp <- subset(df, Tables %in% input$show_tables)
  
  tmp %>% 
    dplyr::mutate(n = "Yes")%>%
    tidyr::pivot_wider(names_from = Tables, values_from = n, values_fill = list(n = "No"))
  })
  output$mytable1 <- DT::renderDataTable({
    DT::datatable(result())
  })
  
}

shinyApp(ui, server)

-output

Variables	tabla_1	tabla_2	tabla_3	tabla_4
A	Yes	Yes	No	Yes
Z	Yes	No	No	No
Y	Yes	No	No	No
V	Yes	No	No	Yes
B	No	Yes	No	Yes
H	No	Yes	No	No
U	No	Yes	Yes	Yes
S	No	Yes	Yes	No
M	No	No	Yes	No
Q	No	No	No	Yes
O	No	No	No	Yes
F	No	No	No	Yes

Variables	tabla_1	tabla_2	tabla_3	tabla_4
A	Yes	Yes	No	Yes
Z	Yes	No	No	No
Y	Yes	No	No	No
V	Yes	No	No	Yes
B	No	Yes	No	Yes
H	No	Yes	No	No
U	No	Yes	Yes	Yes
S	No	Yes	Yes	No
M	No	No	Yes	No
Q	No	No	No	Yes
O	No	No	No	Yes
F	No	No	No	Yes

R Shiny. No applicable method for 'mutate' applied to an object of class "c('reactiveExpr', 'reactive', 'function')"

1 Answers

Variables	tabla_1	tabla_2	tabla_3	tabla_4
A	Yes	Yes	No	Yes
Z	Yes	No	No	No
Y	Yes	No	No	No
V	Yes	No	No	Yes
B	No	Yes	No	Yes
H	No	Yes	No	No
U	No	Yes	Yes	Yes
S	No	Yes	Yes	No
M	No	No	Yes	No
Q	No	No	No	Yes
O	No	No	No	Yes
F	No	No	No	Yes