how to manipulate dataframe in R shiny app - shiny

Question

Please I need assistant concerning a shiny code. I want to manipulate a data frame input by separating them into column vector for computation but I keep getting this error
Warning in <reactive>(...): NAs introduced by coercion
the code is as follows
library(shiny)
ui <- fluidPage(
# dataset
data <- data.frame(e1 = c(3, 7, 2, 14, 66),
e2 = c(2, 16, 15, 66, 30),
n1 = c(18, 25, 45, 62, 81),
n2= c(20, 30, 79, 64, 89))
# Application title
titlePanel("Demo"),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
# Input: Upload file
fileInput(inputId = 'file', label = 'upload the file')
),
# Display Output
mainPanel(
uiOutput("final")
)
)
)
# Define server logic required to draw a histogram
server <- function(input, output) {
# separating the dataframe into 4 column vectors
e1 <- reactive(as.numeric(input$file[,1]))
e2 <- reactive(as.numeric(input$file[,2]))
n1 <- reactive(as.numeric(input$file[,3]))
n2 <- reactive(as.numeric(input$file[,4]))
# File Upload function
data <- reactive({
file1 <- input$file
if(is.null(file1)){return()}
read.table(file = file1$datapath, sep = ',', header = TRUE)
})
output$result <- renderUI({
y <- (e1()/n1()) - (e2()/n2())
lg_y <- log(y)
v2 <- ((n1() - e1())/e1() * n1()) + ((n2() - e2())/e2() * n2())
w <- 1/v2
w1 <- sum(w)
w2 <- sum(w^2)
c <- w1 - (w2/w1)
s2 <- w * lg_y
ybar <- sum(s2)/sum(w)
Q <- sum(w*((lg_y - ybar)^{2}))# Cochrane homogeneity test statistic
Q.pval <- reactive(pchisq(Q, k() - 1,lower.tail = FALSE))
Isqd <- max(100*((Q-(k()-1))/Q),0)
})
}
# Run the application
shinyApp(ui = ui, server = server)
I have searched almost every question on this forum and haven't seen where the question was answered. please I look forward to your help

Answer 1

Still can't run the code above because you don't define function k(). Also FYI, your renderUI is set for "result" but your uiOutput is set for "final".
You get the warning Warning in <reactive>(...): NAs introduced by coercion because your true data set probably includes a non-numeric in it. I did not get any issues with the data set you provided above.
There are a couple ways forward:
1) Write a function to remove all non-numerics before you process the data. See here for a few examples.
2) Just keep the warning, it is a warning after all so it won't stop your code from running. Currently it turns your non-numerics into NA
3) Use suppressWarnings() but that is usually not recommended.
I do have a suggestion to clean up your code though:
# File Upload function
data <- reactive({
file1 <- input$file
if(is.null(file1)){return()}
read.table(file = file1$datapath, sep = ',', header = TRUE, stringsAsFactors = FALSE)
})
# separating the dataframe into 4 column vectors
e1 <- reactive(as.numeric(data()[,1]))
e2 <- reactive(as.numeric(data()[,2]))
n1 <- reactive(as.numeric(data()[,3]))
n2 <- reactive(as.numeric(data()[,4]))