#
# From Automatic Control Systems, fourth ed.,
# figure 6-14
# transient response of a second-order system
# to a unit step input function
#
damp(t) = exp(-s*wn*t)/sqrt(1.0-s*s)
per(t) = sin(wn*sqrt(1.0-s**2)*t-atan(-sqrt(1.0-s**2)/s))
c(t) = 1-damp(t)*per(t)
#
# wn is natural undamped frequency
# s is damping factor
#
wn = 1.0
set xrange [0:13]
set samples 50
set dummy t
#
# plot c(t) for several different damping factors s
#
plot s=.1,c(t),s=.3,c(t),s=.5,c(t),s=.7,c(t),s=.9,c(t),\
s=1.0,c(t),s=1.5,c(t),s=2.0,c(t)
GNUPLOT 提供使用者设定参数，让使用者可绘出不同参数值下函数图形的变化。