Let's move on to the "messy" strcuture API

Question

I retrieve data from an online database (REDcap) through an API, and the data is delivered as a comma-separated string like this,

RAW.API <- structure("id,event_arm,name,dob,pushed_text,pushed_calc,complete\n\"01\",\"event_1_arm_1\",\"John\",\"1979-05-01\",\"\",\"\",2\n\"01\",\"event_2_arm_1\",\"John\",\"2012-09-02\",\"abc\",\"123\",1\n\"01\",\"event_3_arm_1\",\"John\",\"2012-09-10\",\"\",\"\",2\n\"02\",\"event_1_arm_1\",\"Mary\",\"1951-09-10\",\"def\",\"456\",2\n\"02\",\"event_2_arm_1\",\"Mary\",\"1978-09-12\",\"\",\"\",2\n", "`Content-Type`" = structure(c("text/html", "utf-8"), .Names = c("", "charset"))) 

I have this script that parses it perfectly in a data frame,

 (df <- read.table(file = textConnection(RAW.API), header = TRUE, sep = ",", na.strings = "", stringsAsFactors = FALSE)) id event_arm name dob pushed_text pushed_calc complete 1 1 event_1_arm_1 John 1979-05-01 <NA> NA 2 2 1 event_2_arm_1 John 2012-09-02 abc 123 1 3 1 event_3_arm_1 John 2012-09-10 <NA> NA 2 4 2 event_1_arm_1 Mary 1951-09-10 def 456 2 5 2 event_2_arm_1 Mary 1978-09-12 <NA> NA 2 

Then I do some calculations and write them to pushed_text and pushed_calc , after which I need to format the data back into a comma-separated random structure into which it belongs.

I imagine something like this,

 API.back <- `some magic command`(df, ...) identical(RAW.API, API.back) [1] TRUE 

Some command that can format my data from the data frame I created, df , back to the structure to which the raw API object came, RAW.API .

Any help would be greatly appreciated.

Answer 1

It works:

 some_magic <- function(df) { ## Replace NA with "", converting column types as needed df[] <- lapply(df, function(X) { if(any(is.na(X))) {X[is.na(X)] <- ""; X} else {X} }) ## Print integers in first column as 2-digit character strings ## (DO NOTE: Hardwiring the number of printed digits here is probably ## inadvisable, though needed to _exactly_ reconstitute RAW.API.) df[[1]] <- sprintf("%02.0f", df[[1]]) ## Separately build header and table body, then suture them together l1 <- paste(names(df), collapse=",") l2 <- capture.output(write.table(df, sep=",", col.names=FALSE, row.names=FALSE)) out <- paste0(c(l1, l2, ""), collapse="\n") ## Reattach attributes att <- list("`Content-Type`" = structure(c("text/html", "utf-8"), .Names = c("", "charset"))) attributes(out) <- att out } identical(some_magic(df), RAW.API) # [1] TRUE