Interactive Regression Model not outputting model summary - shiny

Question

I am attempting to run a regression that allows users to determine regression inputs, and then provide an output that is the regression summary. For whatever reason, the output is not coming out correct, and I have looked everyone on the internet to find a solution. I am hoping somebody can help.
For clarification, this is in shiny.
Here is my server code:
shinyServer(
function(input,output,session) {
mod <- eventReactive(input$analysis,{
response <- data[,2]
explan1 <- data[,input$Explan1]
explan2 <- data[,input$Explan2]
explan3 <- data[,input$Explan3]
mod1 <- lm(response~explan1+explan2+explan3)
} )
output$modelSummary <- renderPrint({
(summary(mod()$mod1))
})
output$ColumnNames <- renderPrint({
as.data.frame(colnames(data))
})
}
)
summary(model)
And my ui code
shinyUI(
fluidPage(
titlePanel("What does it take for a Hockey Team to Win?"),
titlePanel("Please select the column numbers for three variables to regress on"),
sidebarLayout(
sidebarPanel(
verbatimTextOutput("ColumnNames"),
numericInput("Explan1","Explanatory Variable 1",3,min = 3, max = 13),
numericInput("Explan2","Explanatory Variable 2",4,min = 3,max = 13),
numericInput("Explan3","Explanatory Variable 3",5,min = 3, max = 13)
),
mainPanel(
actionButton("analysis","Analyze!"),
verbatimTextOutput("modelSummary")
)
)
)
)
When I run the app, select the input columns (which are by number rather than name. I hope to fix this later) and click analyze, I get the following output:
Length Class Mode
0 NULL NULL
I haven't been able to find much relevant information on this output. I hope you all can help.
Thank you in advance.

Answer 1

You're just calling the reactive incorrectly, it should be: summary(mod()) instead of summary(mod()$mod1). Reactives behave very much like functions the way that they return objects.
Here is a fully reproducible example, with an example on how to use a formula instead of individually selecting the columns:
col_names <- names(mtcars)
ui <- fluidPage(
sidebarPanel(
verbatimTextOutput("ColumnNames"),
selectInput("Response", "Response Variable", choices = col_names, selected = "mpg"),
selectInput("Explan1","Explanatory Variable 1", choices = col_names, selected = "cyl"),
selectInput("Explan2","Explanatory Variable 2", choices = col_names, selected = "disp"),
selectInput("Explan3","Explanatory Variable 3", choices = col_names, selected = "wt")
),
mainPanel(
actionButton("analysis","Analyze!"),
verbatimTextOutput("modelFormula"),
verbatimTextOutput("modelSummary")
)
)
server <- function(input, output, session) {
myformula <- reactive({
expln <- paste(c(input$Explan1, input$Explan2, input$Explan3), collapse = "+")
as.formula(paste(input$Response, " ~ ", expln))
})
mod <- eventReactive(input$analysis, {
lm(myformula(), data = mtcars)
})
output$modelFormula <- renderPrint({
myformula()
})
output$modelSummary <- renderPrint({
summary(mod())
})
}
shinyApp(ui, server)
Screenshot: