# Plotting x = x(t), y = y(t)

The following code is extracted from program simdem10 in the Simdem package, and it illustrates how easy it is to plot a curve in the parametric form x = x(t), y = y(t), where x and y are double precision arrays. Of course, the arrays x, and y do not need to be in parameteric form, and any number of up to 4 x,y pairs in the form y = f(x) can be plotted. Setting l(i) = m(i) = 0 suppresses the plotting of y(i).

```
c
c Define line and symbol types and number of points
c
l1 = 1     !solid line type
l2 = 2     !dashed line type
l3 = 3     !dotted line type
l4 = 4     !dashed-dotted line type
m1 = 5     !circle symbol type
m2 = 8     !triangle symbol type
m3 = 11    !square symbol type
m4 = 14    !diamond symbol type
n = nmax/2 !numer of points for plotting
n1 = n
n2 = n
n3 = n
n4 = n
c
c Define the data
c
delta = pi2/(dble(n) - one)
t(1) = zero
do i = 2, n - 1
t(i) = t(i - 1) + delta
enddo
t(n) = pi2
do i = 1, n
cosi = cos(t(i))
sini = sin(t(i))
x1(i) = a*cosi
x2(i) = b*cosi
x3(i) = c*cosi
x4(i) = d*cosi
y1(i) = a*sini
y2(i) = b*sini
y3(i) = c*sini
y4(i) = d*sini
enddo
c
c Define the title and legends
c
ptitle = 'y = f(x)'
xtitle = 'x'
ytitle = 'y'
c
c Plot the graphs
c
call gks004 (l1, l2, l3, l4,
+             m1, m2, m3, m4,
+             n1, n2, n3, n4,
+             x1, x2, x3, x4,
+             y1, y2, y3, y4,
+             ptitle, xtitle, ytitle,
+             axes, gsave)

```

The following plot is then displayed and can be edited to add further features, printed, or archived as a graphics file.