# Fortran help

#### kathrynag

I am doing a problem with calculating orbits.
The orbit can be expressed in polar coordinates as r=p/(1-ecos(theta)) where r and theta are the distance and angle of the satellite from the center of the earth, p is a paremter where p=1200 km, and e is a parameter representing eccentricity.
I'm supposed to write a program to calculate the distance of the satellite from the earth as a function of theta if the satellite has an eccentrity of 0, .25, .5, .75, and 1.
Write the program to input values of e and theta. Here is what I have done:

program calculating_orbits
implicit none
real :: r !distance of the satellite from the center of the earth
real :: theta !angle of the satellite from the center of the earth
real, parameter :: p=1200 !parameter specifying the size of the orbit
real :: e !parameter specifying the eccentricity of the orbit
write (*,*) 'This program accepts inputs of theta and e and outputs the
+ value of r=p/(1-e*cos(theta)).'
write (*,*) 'This program will run until a number not in the domain
+ is inputted.'
do
write (*,*) 'Please input a real number.'
Now I get stuck. Any hints?

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#### mathmate

r=p/(1-e*cos(theta))
can you try to write this in fortran and print r as your result?

#### akshaythegeek

Few questions in fortran :)
1. Which is the best plotting tool in fortran
2. How to get out put in form of .dat files in fortran
3. Can any one post a code for calculating floating point operations and finally plotting it..I read so many papers i never able to understand how they plot those

#### minger

1. Which is the best plotting tool in fortran
If you're using *NIX, you can use XMGRACE. Typically I just write a file which can be easily read into Excel.

2. How to get out put in form of .dat files in fortran
You can write in any form you want. I don't understand.

3. Can any one post a code for calculating floating point operations and finally plotting it..I read so many papers i never able to understand how they plot those
Code:
OPEN(11,file='output_file.dat',form='formatted')
DO i=1,10
x = REAL(i)
y = x**2
WRITE(11,*) x,y
END DO
CLOSE(11)

#### akshaythegeek

What about calculating floating point operation, suppose i have a mac and i am running a program then how to compare two programs ..how to plot graphs between floating point operations ......between these two programs

"Fortran help"

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