Mean Line in GNUPlot

I'm trying to get the average response time in my graph of apache requests and response times.

Sampl开发者_Go百科e data:

11/May/2011:17:34:55 2
11/May/2011:17:34:56 38
11/May/2011:17:34:56 2
11/May/2011:17:34:56 493
11/May/2011:17:34:56 2
11/May/2011:17:34:57 281

The data is graphed using this:

plot "input.dat" using 1:2

What I want is line in the center of the average response time for every X value.

Sample Graph:

http://i.min.us/jlcmbY.png

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This blog post shows how to analyze access log with moving mean in gnuplot and preprocess data with awk to get totals for every second.