How do you custom format opencpu output - opencpu

Question

I have a csv file like this:
DateTime Server1 Server2 Server3
8/24/2014 15:20 6.09 5.7 5.21
8/24/2014 15:55 4.54 4.38 5.33
8/24/2014 16:04 5.03 4.52 4.92
8/24/2014 16:18 4.93 4.61 5.56
8/24/2014 16:27 6.27 4.18 5.62
8/24/2014 16:42 4.59 4.61 6.73
8/24/2014 16:56 5.91 4.37 4.76
8/24/2014 17:10 4.53 4.3 4.59
I used ocpu platfrom to upload it. The R function to read the csv file is this:
readcsvnew <- function(file, ...){
if(!grepl(".csv$", file)){
stop("Uploaded file must be a .csv file!")
}
read.csv(file, header=TRUE, ...);
}
Once I read this file using ocpu, the data is in the session. Now I need to make a call to update my html list. To do this, I need to make a call to the session object and retrieve the header in json format:
<legend>Plot Parameters</legend>
<label>Y-Axis</label>
<select id="yaxis" multiple="multiple">
</select>
<label>X-Axis</label>
<select name="xaxis" id="pollutant">
</select>
Once I get the header in Json, I can populate it with javascript. Now that select list are updated, based on user picked values of x-axis (this will be DateTime) and Y-axis values (this could be Server1 or Server1 thru Server3), I need to make another call to session and retrieve the values in custom Json format as follows:
{"name":"Server1","data":[[1408893651000,6.09],[1408895711000,4.54]},{"name":"Server2","data":[[1408893651000,5.7],[1408895711000,4.38]},{"name":"Server3","data":[[1408893651000,5.21],[1408895711000,5.33]}

Answer 1

If you retrieve the output of an object, HTTP GET parameters are mapped to jsonlite::toJSON(). For example:
http://public.opencpu.org/ocpu/library/datasets/data/iris/json
http://public.opencpu.org/ocpu/library/datasets/data/iris/json?dataframe=columns
http://public.opencpu.org/ocpu/library/datasets/data/iris/json?digits=0
http://public.opencpu.org/ocpu/library/datasets/data/iris/json?dataframe=columns&digits=0
See this email for a worked example of using the 2 step process to retrieve output from an RPC request using custom JSON.
Alternatively you can make your function return a list instead of a data frame using as.list.