Flexible upload data to Shiny-server

There is a function called fileInput comes with Shiny-server, which can upload data to server. In this post, I would like to share my experience of uploading different kind of data (.txt, .csv, .xls, .xlsx, etc.) to Shiny-server.

The idea of flexible uploading data is: using File Selection Dialog to determine the format and location of target document, create different uploading control panel for corresponding format, then upload data using corresponding R package and command. Due to there could be a great number of arguments for an uploading function, e.g. read.table has more than 20 arguments, I included only the most frequently used arguments, such as header, sep, etc. and take the rest as a character string, so users can type the code they needed themselves.

Open the above application in a new tab.

The flexibility of arguments input was achieved through executing a string as a command:

eval(parse(text = expr))

where expr is a string of command, e.g. ‘read.table(file, header = TRUE)’. The function parse was suggested to be carefully used by Thomas Lumley, however, I don’t know why and I have no alternative choice.

Loading required package: fortunes
If the answer is parse() you should usually rethink the question.
   -- Thomas Lumley
      R-help (February 2005)

The source code of ui.R and server.R can be downloaded.

Written on August 5, 2013