no word report creation with R & Shiny (R studio) - r

Question

I created a R shiny application for stats analyses. I'd like that app allowed users to download a word report. I use the code on the shiny website gallery - http://shiny.rstudio.com/gallery/download-knitr-reports.html.
Server
shinyServer(function(input, output) {
regFormula <- reactive({
as.formula(paste('mpg ~', input$x))
})
output$regPlot <- renderPlot({
par(mar = c(4, 4, .1, .1))
plot(regFormula(), data = mtcars, pch = 19)
})
output$downloadReport <- downloadHandler(
filename = function() {
paste('my-report', sep = '.', switch(
input$format, PDF = 'pdf', HTML = 'html', Word = 'docx'
))
},
content = function(file) {
src <- normalizePath('report.Rmd')
# temporarily switch to the temp dir, in case you do not have write
# permission to the current working directory
owd <- setwd(tempdir())
on.exit(setwd(owd))
file.copy(src, 'report.Rmd')
library(rmarkdown)
out <- render('report.Rmd', switch(
input$format,
PDF = pdf_document(), HTML = html_document(), Word = word_document()
))
file.rename(out, file)
}
)
})
UI
library(shiny)
shinyUI(fluidPage(
title = 'Download a PDF report',
sidebarLayout(
sidebarPanel(
helpText(),
selectInput('x', 'Build a regression model of mpg against:',
choices = names(mtcars)[-1]),
radioButtons('format', 'Document format', c('PDF', 'HTML', 'Word'),
inline = TRUE),
downloadButton('downloadReport')
),
mainPanel(
plotOutput('regPlot')
)
)
))
It works fine and I can download the report on the web app. I use the proposed code in R studio on a OS X computer and it works fine too. I try to do the same with R studio on a win 7 computer but it doesn't works, the report (html, pdf or docx) is not created whereas the apps works fine.
Can someone help me ?
Ari