Create data with function inside shinyServer to feed ggplot

Question

I have a Shiny app what calculates some power estimates for a type of genetic association study. The ui.R is pretty simple, and the server.R has a function that gives a data frame (I think I can't have this function as `reactive` because it has some parameters). The link to the Gist is here. To run it: ``` library(shiny) shiny:: runGist('5895082') ``` The app calculates correctly the estimates, but I have two questions regarding it: Is it possible to have the `output$powTable` actually represent all the values contained within the range, in the first `sliderInput(n.cases)`?. It only seems to represent the two extreme values of the range... what I'm doing wrong? There's an error when running the app: `Error: Reading objects from shinyoutput object not allowed.` How can I pass the data (reactivity?) from the function `f()` to feed the ggplot? After much trial and error, I am very lost. Where can be the error in my code? Many thaks in advance! The original code of the function works well…

Accepted Answer

First of all, you have `n.cases` named inconsistently I think. It's `n.cases` sometimes, and `ncases` other times. Is that a mistake?

Anyway, `output$mydata()` is incorrect. It isn't an output. It should be just:

```
mydata <- reactive(f(input$n.cases,
  input$p0,
  input$OR.cas.ctrl,
  input$Nh,
  input$sig.level))
```

And then when executing it in `output$powHap()` it should be:

```
output$powHap <- renderPlot(
{
   print(ggplot(data = mydata(), aes(ncases, power)) + 
     theme_bw() + 
     theme(text=element_text(family="Helvetica", size=12)) + 
     labs(title = "Ad-hoc power for haplogroup") +
     scale_color_brewer(palette = "Dark2", guide = guide_legend(reverse=TRUE)) +
     xlab("number of cases/controls") +
     ylab("power") +
     scale_x_log10() +
     geom_line(alpha=0.8, size=0.2) +
     geom_point(aes(shape = factor(OR)), colour="black"))
})
```

The important part there is that you need to do:

```
data = mydata()
```

rather than

```
data = output$mydata
```

Because `output$mydata` is a (reactive) function.

I would suggest reading the documentation on how reactives work. The whole thing should make a lot more sense afterwards. +1 for a very reproducible example by the way. This is how all questions should be posted.

Create data with function inside shinyServer to feed ggplot

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