added diff2.awk to estimate numerical second diff;

removed commented out population covariance from cov.awk;
added decimal points to pi estimate in em.awk;

1 files changed, 1 insertions, 0 deletions

diff --git a/diff.awk b/diff.awk
index 2b42a2d..1e6a882 100644
--- a/diff.awk
+++ b/diff.awk
@@ -2,6 +2,7 @@
 
 ### diff.awk
 # print numerical diff along columns
+# dy[n] = y[n] - y[n-1]
 
 
 BEGIN {