Problems with "observe" in Shiny - r

Question

I am working in a ShinyApp which objective here is to create a selection based on attributes that are generated from an Excel database (the number of attributes may vary). Below is the most important part of my server.R code:
shinyServer(function(input, output, session){
seleciona_planilha <- observe({
dados = input$arquivo
if (is.null(dados))
{
return(NULL)
}
else
{
capturar = names(getSheets(loadWorkbook(dados$datapath)))
updateSelectInput(session,"planilha",choices = capturar)
}
})
carrega_dados <- reactive({
dados = input$arquivo
if (is.null(dados))
{
return(NULL)
}
else{return(read.xlsx(dados$datapath, sheetName = input$planilha))}
})
The first "observe" function above works well in order to select the correct sheet and proceed to analysis with the code below.
rotina <- reactive({
dados = carrega_dados()
tam_dados = length(dados)
pos_ini = 22
vet_comp = vector()
resultados = as.data.frame(matrix(nrow = length(seq(pos_ini,tam_dados,2)), ncol = 10))
nomes = names(dados)
cd = 4
k = 1
amostra = vector()
for(i in 1:length(dados[,1]))
{
if(dados[i,6] == 1)
{
amostra[1] = as.character(dados[i,7])
break
}
}
for(i in 1:length(dados[,1]))
{
if(dados[i,6] == 2)
{
amostra[2] = as.character(dados[i,7])
break
}
}
names(resultados) = c("Name",amostra[1], amostra[2],"NSD",
"Tau","Var(Tau)","D-Prime",
"Var(D-Prime)","IC(D-Prime)","p-value(D-Prime)")
for(i in seq(pos_ini,tam_dados,2))
{
cNSD = 0
c1 = 0
c2 = 0
for(j in 1:length(dados[,i]))
{
if(as.character(dados[j,i]) == " NSD" || as.character(dados[j,i]) == "NSD")
{
cNSD = cNSD + 1
}
if(as.character(dados[j,i]) == "1")
{
c1 = c1 + 1
}
if(as.character(dados[j,i]) == "2")
{
c2 = c2 + 1
}
}
vet_comp = c(c1,cNSD,c2)
resultados[k,1] = nomes[i]
resultados[k,2] = c1
resultados[k,3] = c2
resultados[k,4] = cNSD
resultados[k,5] = round(twoAC(vet_comp)$coefficients[1,1],cd)
resultados[k,6] = round((twoAC(vet_comp)$coefficients[1,2])^2,cd)
resultados[k,7] = round(twoAC(vet_comp)$coefficients[2,1],cd)
resultados[k,8] = round((twoAC(vet_comp)$coefficients[1,2])^2,cd)
if(vet_comp[1] != 0 && vet_comp[2] != 0 && vet_comp[3] != 0)
{
resultados[k,9] = paste("[",round(twoAC(vet_comp)$confint[,1],cd),";",
round(twoAC(vet_comp)$confint[,2],cd),"]")
}
else
{
resultados[k,9] = paste("No IC")
}
resultados[k,10] = round((twoAC(vet_comp)$p.value)/2,cd)
k = k + 1
}
return(resultados)
})
The reactive function "rotina" returns a data.frame. The first column in the data.frame are the attribute names that I would like to use in a selector.
But for some reason I don't know, when I call another "observe" function to get the attribute names and pass to the selector, it not works.
seleciona_atributo <- observe({
resultados = rotina()
atributos = resultados[,1]
updateSelectInput(session,"atributo",choices = atributos)
})
I tried to assign "resultados" as a global variable too, but with no success.
Finally, my ui.R code:
shinyUI(fluidPage(
titlePanel("2-AC Sensory Tool"),
sidebarLayout(
sidebarPanel(
fileInput('arquivo', 'Choose XLS/XLSX File',
accept=c('.xls','.xlsx')),
tags$hr(),
selectInput("planilha",label = h4("Select data sheet"),""),
tags$hr(),
selectInput("atributo",label = h4("Select attribute to generate d-prime graphic",""),
downloadButton('download', 'Download results')
),
mainPanel(
plotOutput("grafico_dp"),
plotOutput("grafico_dist"),
h4("Results Table"),
dataTableOutput("saida")
)
)
))
Thanks in advance!