#

# This script demonstrates the use of assignment operators and

# sequential expression evaluation to track data points as they

# are read in.

#

# We use the '=' and ',' operators to track the running total

# and previous 5 values of a stream of input data points.

#

# Ethan A Merritt - August 2007

#

# Define a function to calculate average over previous 5 points

#

set title \

    "Demonstrate use of assignment and serial evaluation operators\n" \

    . "to accumulate statistics as successive data lines are read in\n"

set key invert box center right reverse Left

set xtics nomirror

set ytics nomirror

set border 3

samples(x) = $0 > 4 ? 5 : ($0+1)

avg5(x) = (shift5(x), (back1+back2+back3+back4+back5)/samples($0))

shift5(x) = (back5 = back4, back4 = back3, back3 = back2, back2 = back1, back1 = x)

#

# Initialize a running sum

#

init(x) = (back1 = back2 = back3 = back4 = back5 = sum = 0)

#

# Plot data, running average and cumulative average

#

datafile = 'silver.dat'

set xrange [0:57]

set style data linespoints

plot sum = init(0), \

     datafile using 0:2 title 'data' lw 2 lc rgb 'forest-green', \

     '' using 0:(avg5($2)) title "running mean over previous 5 points" pt 7 ps 0.5 lw 1 lc rgb "blue", \

     '' using 0:(sum = sum + $2, sum/($0+1)) title "cumulative mean" pt 1 lw 1 lc rgb "dark-red"

pause -1 "Hit return to continue"

reset