see: https://groups.google.com/forum/#!topic/shiny-discuss/P74Ch8xHW_4

server.R

# server.R

shinyServer(
  function(input, output) {

    # data frame with colnames
    df <- data.frame(matrix(0, 1, 2))
    colnames(df) <- c("First Column","Second Column") 

    # table with column headers
    output$df <- renderTable({df}
      , include.rownames = FALSE
      , include.colnames = TRUE
      , sanitize.text.function = function(x) x
    )  

    # this one doesn't work
    output$table <- renderTable({df}
      , include.rownames = FALSE
      , include.colnames = TRUE
      , sanitize.text.function = function(x) x
    )  
  }
)

ui.R

# ui.R

library("shiny")
#library('devtools')
#install_github('shiny-incubator', 'rstudio')
library("shinyIncubator")

# initialize data with colnames
df <- data.frame(matrix(0, 1, 2))
colnames(df) <- c("First Column","Second Column") 

shinyUI(
  pageWithSidebar(
  
    headerPanel('Simple matrixInput example')
    ,
    sidebarPanel(
    
      tableOutput(outputId = 'df')
      ,
      matrixInput(inputId = 'data', label = 'Add/Remove Rows', data = df)
    )
    ,
    mainPanel(
      tableOutput(outputId = 'table')
    )
  )
)