Shiny plot doesn't change with inputs - r

Question

I am an absolute beginner to Shiny, so I would appreciate your patience and any advice to my issue. Here's the server function that I'm using to output a ggplot, which works on its own, but doesn't change at all when I change the inputs:
server <- function(input, output) {
output$plooot<-renderPlot({
df = df %>%
group_by(input$Category,Type) %>%
summarise(Distribution=sum(Distribution))
ggplot(df,aes(input$Category,Distribution,fill=Type))+geom_bar(stat="identity",position="dodge")})
}
shinyApp(ui=ui,server=server)
Here's my ui function as well just for reference:
ui <- fluidPage(
titlePanel("chart"),
# Generate a row with a sidebar
sidebarLayout(
# Define the sidebar with one input
sidebarPanel(
selectInput("Category","Category:",choices=c("a","b","c","d","e","f")),
selectInput("a","a:", choices=unique(Table$a), selected="All"),
selectInput("b","b:", choices=unique(Table$b), selected="All"),
selectInput("c","c:", choices=unique(Table$c), selected="All"),
selectInput("d","d:", choices=unique(Table$d), selected="All"),
selectInput("e","e:", choices=unique(Table$e), selected="All"),
selectInput("f","f:", choices=unique(Table$f), selected="All")
),
# Create a spot for the barplot
mainPanel(
plotOutput("plooot")
)
)
)
Unfortunately, I can't post the data for legal reasons, but here are two plots of what I want vs. what I have:
This is probably a very rudimentary mistake, but I'm having trouble understanding what I'm doing wrong.

Answer 1

I agree with #AndS., re-assigning back to df = ... is not likely what you want/need but will almost certainly irreversibly reduce your data. Additionally, input$Category is a character and not a symbol that group_by is expecting. Try this:
library(shiny)
library(dplyr)
library(ggplot2)
ui <- fluidPage(
titlePanel("chart"),
# Generate a row with a sidebar
sidebarLayout(
# Define the sidebar with one input
sidebarPanel(
selectInput("Category","Category:",choices=colnames(mtcars))
),
# Create a spot for the barplot
mainPanel(
plotOutput("plooot")
)
)
)
server <- function(input, output) {
output$plooot<-renderPlot({
req(input$Category)
icq <- sym(input$Category)
mtcars %>%
group_by(!!!icq, vs) %>%
summarise(disp=sum(disp)) %>%
ggplot(aes_string(input$Category, "disp", fill="vs")) +
geom_bar(stat="identity", position="dodge")
})
}
shinyApp(ui=ui,server=server)

Answer 2

Not knowing what your data looks like, see below. The best thing to do is for any data set that will be affected by a user input, is to put it in a reactive expression. Then use that reactive expression in your output plots. I also added an "ALL" to your choices and an if function in case you want to see them all together like you have in your picture.
ui <- fluidPage(
titlePanel("Chart"),
sidebarLayout(
sidebarPanel(
selectInput("Category","Category:",choices=c("All","a","b","c","d","e","f"))
),
mainPanel(
plotOutput("Plot")
)
)
)
server <- function(input, output) {
Distribution <- c(1,2,3,4,1,2,3,5,2,4)
Category <- c("a","b","c","e","f","a","b","c","e","f")
Type <- c("Blue","Blue","Blue","Blue","Blue","Red","Red","Red","Red","Red")
df <- data.frame(Distribution ,Category,Type)
df_subset <- reactive({
if (input$Category == "All") {df}
else{df[df$Category == input$Category,]}
})
output$Plot <- renderPlot({
dat <- df_subset()
dat <- dat %>%
group_by(Category,Type) %>%
summarise(Distribution=sum(Distribution))
plot <- ggplot(dat,aes(Category,Distribution,fill=Type))+geom_bar(stat="identity",position="dodge")
return(plot)
})
}
shinyApp(ui=ui,server=server)