1 files changed, 42 insertions, 1 deletions
diff --git a/help/en_US/xcov1.xml b/help/en_US/xcov1.xml
index 7a866bb..3872563 100644
--- a/help/en_US/xcov1.xml
+++ b/help/en_US/xcov1.xml
@@ -17,7 +17,48 @@
 
   <refnamediv>
     <refname>xcov1</refname>
-    <refpurpose></refpurpose>
+    <refpurpose>Compute covariance at various lags [=correlation(x-mean(x),y-mean(y))].</refpurpose>
   </refnamediv>
 
+
+<refsynopsisdiv>
+   <title>Calling Sequence</title>
+   <synopsis>
+   [R, lag] = xcov (X)
+   ... = xcov (X, Y)
+   ... = xcov (..., maxlag)
+   ... = xcov (..., scale)
+   </synopsis>
+</refsynopsisdiv>
+
+<refsection>
+   <title>Parameters</title>
+   <variablelist>
+   <varlistentry><term>X:</term>
+      <listitem><para> Input vector</para></listitem></varlistentry>
+   <varlistentry><term>Y:</term>
+      <listitem><para> if specified, compute cross-covariance between X and Y, otherwise compute autocovariance of X.</para></listitem></varlistentry>
+   <varlistentry><term>maxlag:</term>
+      <listitem><para> is specified, use lag range [-maxlag:maxlag], otherwise use range [-n+1:n-1].</para></listitem></varlistentry>
+   <varlistentry><term>scale:</term>
+      <listitem><para> </para></listitem></varlistentry>
+   <varlistentry><term>'biased':</term>
+      <listitem><para> for covariance=raw/N,</para></listitem></varlistentry>
+   <varlistentry><term>'unbiased':</term>
+      <listitem><para> for covariance=raw/(N-|lag|),</para></listitem></varlistentry>
+   <varlistentry><term>'coeff':</term>
+      <listitem><para> for covariance=raw/(covariance at lag 0),</para></listitem></varlistentry>
+   <varlistentry><term>'none':</term>
+      <listitem><para> for covariance=raw</para></listitem></varlistentry>
+   <varlistentry><term>'none':</term>
+      <listitem><para> is the default.</para></listitem></varlistentry>
+   </variablelist>
+</refsection>
+
+<refsection>
+   <title>Description</title>
+   <para>
+Compute covariance at various lags [=correlation(x-mean(x),y-mean(y))]. Returns the covariance for each lag in the range, plus an optional vector of lags.
+</para>
+</refsection>
 </refentry>