#

# Show use of pseudodata mechanism '+' to use plot styles with more than 

# one relevant value per x coordinate. In this example we use the style

# "filledcurves" to show the difference between two analytic functions.

# This corresponds to the specification of multiple columns in the 

# 'using' option for input from data files.

# 

#

approx_1(x) = x - x**3/6

approx_2(x) = x - x**3/6 + x**5/120 

approx_3(x) = x - x**3/6 + x**5/120 - x**7/5040

label1 = "x - {x^3}/3!"

label2 = "x - {x^3}/3! + {x^5}/5!"

label3 = "x - {x^3}/3! + {x^5}/5! - {x^7}/7!"

#

set termoption enhanced

save_encoding = GPVAL_ENCODING

set encoding utf8

#

set title "Polynomial approximation of sin(x)"

set key Left center top reverse

set xrange [ -3.2 : 3.2 ]

set xtics ("-π" -pi, "-π/2" -pi/2, 0, "π/2" pi/2, "π" pi)

set format y "%.1f"

set samples 500

set style fill solid 0.4 noborder

plot '+' using 1:(sin($1)):(approx_1($1)) with filledcurve title label1 lt 3, \

     '+' using 1:(sin($1)):(approx_2($1)) with filledcurve title label2 lt 2, \

     '+' using 1:(sin($1)):(approx_3($1)) with filledcurve title label3 lt 1, \

     sin(x) with lines lw 1 lc rgb "black"

pause -1 "Hit return to continue"

set encoding save_encoding

reset