--- imach096d/doc/imach.htm	2002/03/11 15:24:05	1.9
+++ imach096d/doc/imach.htm	2002/03/11 22:26:00	1.10
@@ -1,4 +1,4 @@
-<!-- $Id: imach.htm,v 1.9 2002/03/11 15:24:05 brouard Exp $ --!>
+<!-- $Id: imach.htm,v 1.10 2002/03/11 22:26:00 brouard Exp $ --!>
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 <head>
@@ -430,9 +430,40 @@ a large stepm i.e stepm=12 or 24 and the
 stepm=1 month. If newstepm is the new shorter stepm and stepm can be
 expressed as a multiple of newstepm, like newstepm=n stepm, then the
 following approximation holds: 
-<pre>aij(n stepm) = aij(stepm) +ln(n)
+<pre>aij(stepm) = aij(n . stepm) - ln(n)
 </pre> and
-<pre>bij(n stepm) = bij(stepm) .</pre>
+<pre>bij(stepm) = bij(n . stepm) .</pre>
+
+<p> For example if you already ran for a 6 months interval and
+got:<br>
+ <pre># Parameters
+12 -13.390179  0.126133 
+13  -7.493460  0.048069 
+21   0.575975 -0.041322 
+23  -4.748678  0.030626 
+</pre>
+If you now want to get the monthly estimates, you can guess the aij by
+substracting ln(6)= 1,7917<br> and running<br>
+<pre>12 -15.18193847  0.126133 
+13 -9.285219469  0.048069
+21 -1.215784469 -0.041322
+23 -6.540437469  0.030626
+</pre>
+and get<br>
+<pre>12 -15.029768 0.124347 
+13 -8.472981 0.036599 
+21 -1.472527 -0.038394 
+23 -6.553602 0.029856 
+</br>
+which is closer to the results. The approximation is probably useful
+only for very small intervals and we don't have enough experience to
+know if you will speed up the convergence or not.
+<pre>         -ln(12)= -2.484
+ -ln(6/1)=-ln(6)= -1.791
+ -ln(3/1)=-ln(3)= -1.0986
+-ln(12/6)=-ln(2)= -0.693
+</pre>
+
 <h4><font color="#FF0000">Guess values for computing variances</font></h4>
 
 <p>This is an output if <a href="#mle">mle</a>=1. But it can be
