writing binary data in R

Question

I'm trying to write an HTTP POST request, but I need to get my data into binary format first. This is probably an easy question, but I find R connections really confusing, and I've been having trouble finding a good resource that explains them in a way I understand.

So as an example, say I want to encode an integer (8 byte) and then a numeric (4 byte). Here is the code I've tried:

myint <- as.integer(1339700942)
mydouble <- 1.2
obj <- file(open='w+b') #I've tried textConnection too, but no good
w.int <- writeBin(myint, obj, size=8, endian='big')
w.double <- writeBin(mydouble, obj, size=4, endian='big')

This allowed me to open the connection, but all it wrote was NULL. What is the correct way to use connections and writeBin in a situation like this?

According to ?writeBin it returns NULL unless the con argument is a raw vector, which it is not in your example. It would help if you could give more background on your actual problem. — Joshua Ulrich
– Joshua Ulrich, Commented Jul 20, 2012 at 19:28
The example is very close to my actual problem. I want to post XDR data onto a website, and the format will be a repeating sequence of 8-byte ints and 4-byte floats. — Eli Sander
– Eli Sander, Commented Jul 20, 2012 at 19:32
should I assign 'obj <- raw(0)' instead of opening a connection...? — Eli Sander
– Eli Sander, Commented Jul 20, 2012 at 19:33
I'm really glad you figured out your problem! Would you please write an answer summarizing what worked for you and (after the mandatory waiting period) accept it? That way it's more likely that other people will benefit from what you learned. (As an added incentive, I will check back and up vote your answer...) — joran
– joran, Commented Jul 21, 2012 at 3:42

Eli Sander · Accepted Answer · 2012-07-23 12:46:17Z

4

The object 'obj' is not actually necessary. If writeBin is writing to an R object rather than a file outside of R, the last three lines can be replaced by:

w.int <- writeBin(myint, raw(0), size=8, endian='big')
w.double <- writeBin(mydouble, raw(0), size=4, endian='big')

answered Jul 23, 2012 at 12:46

Eli Sander

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