{"id":628,"date":"2012-10-18T13:40:19","date_gmt":"2012-10-18T13:40:19","guid":{"rendered":"http:\/\/garysieling.com\/blog\/?p=628"},"modified":"2012-10-18T13:40:19","modified_gmt":"2012-10-18T13:40:19","slug":"building-a-statistical-significance-testing-web-service-powered-by-r","status":"publish","type":"post","link":"https:\/\/www.garysieling.com\/blog\/building-a-statistical-significance-testing-web-service-powered-by-r\/","title":{"rendered":"Building a statistical significance testing web service powered by R"},"content":{"rendered":"

R<\/a> is a programming language focused on solving statistical and mathematical calculations. R programs often operate on large<\/a>, in-memory<\/a> data sets<\/a>, which feels somewhat similar to database programming. Examples in the R Cookbook<\/a> bear a resemblence to functional programming in clojure, as others have noted<\/a>.<\/p>\n

I’ve been exploring the language to gain insight into related, but disparate technologies that I use with regularity (e.g. Postgres), but for this to be really useful, I’d like to see R behind a webservice. Looking through the official website, there are many defunct attempts at using R in this manner, often abandoned once the maintainer finishes their masters.<\/p>\n

A couple have survived, notably Rook<\/a> and rApache<\/a>. Rook is a web server inside of R, and rApache, as you might guess, is an Apache module that calls R. I’ve chosen rApache, as I’d like to have a battle-tested front-end for this – while R seems to have very committed maintainers, there do not seem to be very many of them, and I have yet to find examples of anyone running this as a production application.<\/p>\n

Inspired by WolframAlpha’s APIs, I built a small web service to test statistical significance. In the future I intend to do tests on performance and security, as well as available JSON libraries.<\/p>\n

Here is the installation procedure:<\/p>\n

apt-get upgrade\napt-get update\napt-get install r-base r-base-dev \napt-get install apache2-mpm-prefork apache2-prefork-dev \napt-get install git-core\ngit clone https:\/\/github.com\/jeffreyhorner\/rapache.git\ncd rapache\n.\/configure\nmake\nmake test\nmake install\nvi \/etc\/apache2\/httpd.conf<\/pre>\n
Apache configuration settings:<\/p>\n
\n\nLoadModule R_module \/usr\/lib\/apache2\/modules\/mod_R.so\n\n\nSetHandler r-info\n<\/Location>\n\nROutputErrors\n\n\n        SetHandler r-script\n        RHandler sys.source\n<\/Directory>\n\n<\/pre>\n
\/etc\/init.d\/apache2 restart<\/pre>\n
And these are the contents of ws.R:<\/p>\n
\n\nsetContentType(\"application\/json\")\n\nzscore<-function(p, pc, N, Nc){ (p-pc) \n     \/ sqrt(p * (1-p) \/ N + pc * (1-pc) \/ Nc) }\nsignificant<-function(p, pc, N, Nc){ \n     zscore(p, pc, N, Nc) > 1.65 }\n\nvalid<-function(x){ nchar(x) < 10 }\n\nif (!valid(GET$pc) \n || !valid(GET$p) \n || !valid(GET$N) \n || !valid(GET$Nc)) {\n  cat('error:arg length')\n} else {\ncat(significant(as.numeric(GET$p), \n                as.numeric(GET$pc), \n                as.numeric(GET$N), \n                as.numeric(GET$Nc)))\n}\n\nOK\n\n<\/pre>\n
For instance, the output of http:\/\/localhost:8080\/R\/ws.R?p=.15&pc=.10&N=1000&Nc=1100
\nis \"TRUE\"<\/p>\n","protected":false},"excerpt":{"rendered":"
R is a programming language focused on solving statistical and mathematical calculations. R programs often operate on large, in-memory data sets, which feels somewhat similar to database programming. Examples in the R Cookbook bear a resemblence to functional programming in clojure, as others have noted. I’ve been exploring the language to gain insight into related, … <\/p>\n
Continue reading “Building a statistical significance testing web service powered by R”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[4,6,27],"tags":[440,450,452,559,587],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t