Multiple conditional selection criteria in shiny - r

Question

Probably a simple one:
I have a data.frame such as this:
set.seed(1)
df <- data.frame(name=c("A","A","B","C","B","A"),id=1:6,rep1=rnorm(6),rep2=rnorm(6),rep3=rnorm(6))
In the UI part of the R shiny server I'd like to have a drop-down menu that lists unique(df$name), and then given that selection, in a second drop-down menu I'd like to list all df$id that correspond to that df$name selection (i.e., if the selected name is selected.name, this will be: dplyr::filter(df,name == selected.name)$id). Then given these two selections (which are a unique row in df) I'd like to execute server, which executes this function to plot the given selection:
plotData <- function(selected.df)
{
plot.df <- reshape2::melt(dplyr::select(selected.df,-name,-id))
ggplot2::ggplot(plot.df,ggplot2::aes(x=variable,y=value))+ggplot2::geom_point()+ggplot2::theme_minimal()
}
Here's the shiny code I'm trying:
server <- function(input, output)
{
output$id <- renderUI({
selectInput("id", "ID", choices = unique(dplyr::filter(df,name == input$name)$id))
})
output$plot <- renderPlot({
plotData(selected.df=dplyr::filter(df,name == input$name,id == output$id))
})
}
ui <- fluidPage(
# App title ----
titlePanel("Results Explorer"),
# Sidebar layout with a input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# select name
selectInput("name", "Name", choices = unique(df$name)),
uiOutput("id")
),
# Main panel for displaying outputs ----
mainPanel(
plotOutput("plot")
)
)
)
When I run: shinyApp(ui = ui, server = server), I get the error:
Evaluation error: Reading objects from shinyoutput object not allowed..
What's missing?

Answer 1

Here the option would be have renderUI in the 'server' and uiOuput in 'ui'
-ui
library(shiny)
library(dplyr)
library(ggplot2)
ui <- fluidPage(
# App title ----
titlePanel("Results Explorer"),
# Sidebar layout with a input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# select name
selectInput("name", "Name", choices = unique(df$name)),
uiOutput("idselection")
# select id - this is where I need help
),
# Main panel for displaying outputs ----
mainPanel(
# ShinyServer part
plotOutput("plot")
)
)
)
-server
server = function(input, output) {
output$idselection <- renderUI({
selectInput("id", "ID", choices = unique(df$id[df$name ==input$name]))
})
output$plot <- renderPlot({
df %>%
count(name) %>%
ggplot(., aes(x = name, y = n, fill = name)) +
geom_bar(stat = 'identity') +
theme_bw()
})
}
shinyApp(ui = ui, server = server)
-output

Answer 2

Ok, tiny fix:
Create data:
set.seed(1)
df <- data.frame(name=c("A","A","B","C","B","A"),id=1:6,rep1=rnorm(6),rep2=rnorm(6),rep3=rnorm(6))
Function that server will execute:
plotData <- function(selected.df)
{
plot.df <- reshape2::melt(dplyr::select(selected.df,-name,-id))
ggplot2::ggplot(plot.df,ggplot2::aes(x=variable,y=value))+ggplot2::geom_point()+ggplot2::theme_minimal()
}
shiny code:
server <- function(input, output)
{
output$id <- renderUI({
selectInput("id", "ID", choices = unique(dplyr::filter(df,name == input$name)$id))
})
output$plot <- renderPlot({
plotData(selected.df=dplyr::filter(df,name == input$name,id == input$id))
})
}
ui <- fluidPage(
# App title ----
titlePanel("Results Explorer"),
# Sidebar layout with a input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# select name
selectInput("name", "Name", choices = unique(df$name)),
uiOutput("id")
),
# Main panel for displaying outputs ----
mainPanel(
plotOutput("plot")
)
)
)