25.4: Example
- Page ID
- 54409
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This section provides an example program that plots a simple function.
\[ y = \sin(x) \cdot \left( \frac{1 - \cos(x)}{3.0} \right) \nonumber \]
The program, data file, and final output are presented for reference.
Plot Program
The following is an example program that generates points, opens a plot file, write the header, data points, and footer.
program plotExample
implicit none
real, dimension(200) :: x, y
integer :: i, opnstat
! Generate x and y points
do i = 1, 200
x(i) = i * 0.05
y(i) = sin(x(i)) * (1-cos(x(i)/3.0))
end do
! Output data to a file
open (12, file="data.plt", status="replace", &
action="write", position="rewind", &
iostat=opnstat)
if (opnstat > 0) stop "error opening plot file."
! Write header
write (12, '(a)') "# Example Plot File"
write (12, '(a)') "set title ""Example Plot Function"" "
write (12,'(a,a)') "plot ""-"" notitle with dots ",
"linewidth 2 linecolor 2"
! Write points to file.
do i=1,100
write (12,*) x(i), y(i)
end do
! Write footer and close file
write (12, '(a)') "end"
write (12, '(a)') "pause -1"
close(12)
end program plotExample
The data file name can be changed or read from the user.
Plot File
The output file from this program appears as follows:
# Example Plot File
set title "Example Plot Function"
plot "-" notitle with dots linewidth 2 linecolor 2
5.0000001E-02 6.9413913E-06
0.1000000 5.5457884E-05
0.1500000 1.8675877E-04
0.2000000 4.4132397E-04
0.2500000 8.5854460E-04
[many points not displayed due to space considerations]
4.900000 -1.043852
4.950000 -1.048801
5.000000 -1.050716
end
pause -1
The output file can be edited with a standard text editor. This will allow checking the data file for possible errors if it does not display correctly.
Plot Output
The plot output is as follows:
On Windows machines, the plot can be printed by right clicking on the blue bar (on top). This will display a menu, with “Print” as one of the options.