Update readme

Author: lgrz

README.md

@@ -1,3 +1,33 @@
 # Pairwise t-test
 
 Scripts to perform pairwise t-test on TREC run files.
+
+### Requirements
+
+* R
+    * [reshape2][reshape2]
+* [gdeval.pl][gdeval]
+* [trec\_eval][treceval]
+
+[reshape2]: https://cran.r-project.org/web/packages/reshape2/index.html
+[gdeval]: https://github.com/lgrz/trec-web-2013
+[treceval]: https://trec.nist.gov/trec_eval
+
+### Usage
+
+There are two bash scripts to run. First run `pairwise-eval.sh` to evaluate the
+TREC run files. Then run `pairwise-ttest.sh` to compute statistical
+significance.
+
+To compute a pairwise t-test of all run files in the `runs` directory for
+NDCG@10 using `foo.qrels` (which contains the relevance judgments), run
+the following:
+
+```
+./pairwise-eval.sh ndcg 10 foo.qrels runs/*.run
+./pairwise-ttest.sh runs/*.run.ndcg10
+cat result.txt
+```
+
+The `pairwise-eval.sh` script can compute ERR, NDCG and MAP. `gdeval.pl` is
+used for ERR and NDCG, while `trec_eval` is used MAP.