This is a nice command prompt I wrote up a month ago. It's still in the Beta stages however. Anyways, here's a brief overlay of what it does:
1) Takes user input of a function, creates an x/y table and plots it
2) Change the x-range
3) Graph waves (Main thing I wanted to do)

Okay, here's how you use the program:
When ran, you'll enter a prompt:
y = ...
You can type the following commands it knows:
1) help():
- Prints out to the terminal what functions it knows
2) frange(start, end, step):
- Defines the x range. Step can be a float number ie (0.5); useful for the waves because you don't want to see a huge graph of waves; default x range is -100 - 100
3) set(radian):
- Just converts the x-range into a radian range. Takes no arguments
4) polar():
- Change the graph to a polar graph
5) line():
- Change the graph to a line graph (default)
6) show():
- Show the graph

It is beneficial to follow these steps to get it to show correctly:
optional(1) y = frange(0, 10, 0.01))
optional(2) y = line()) or (2) y = polar())
3) show()
4) any functions

All functions have to be completely typed out
Such as the y = 2*(x**2)
Nothing is implied as of now

Sometimes, it'll say that a functions is not recognized even though it already performed it. Don't know why as of yet; if I change the if statements to else if statements, it still does it

Edited 6 Years Ago by hondros: n/a

from numpy import *
from pylab import *

#http://paws.kettering.edu/~drussell/Demos/superposition/superposition.html
#http://catcode.com/trig/trig10.html

def frange(start, end=None, inc=None):
    "A range function, that does accept float increments..."

    if end == None:
        end = start + 0.0
        start = 0.0

    if inc == None:
        inc = 1.0

    L = []
    while 1:
        next = start + len(L) * inc
        if inc > 0 and next >= end:
            break
        elif inc < 0 and next <= end:
            break
        L.append(next)
        
    return L

def funceval(function, numlist=frange(-100, 100, 0.01), splitat='x'):
    y = []
    for x in numlist:
        try:
            numfunction = ''
            for c in function.split(splitat)[:-1]:
                numfunction += c
                numfunction += '(%f)' %(x)
            numfunction += function.split(splitat)[-1]
            y.append(eval(numfunction))
        except:
            numlist.pop(numlist.index(x))
    return y

def ranradians(ran):
    a = []
    for x in ran:
        a.append(radians(x))
    return a

def menuhelp():
    print("Function Plotter v2.0")
    print("Help")
    print("")
    print("Functions can be in any form, so long as there is an 'x'")
    print("Standard form for parabola's typing in the function is:")
    print("A*(x**2)+B*x+C")
    print("Carry this form to any function")
    print("Make sure to type in every symbol, none are implied")
    print("Pi is: pi")
    print("Using sine or similar functions: sin(x)")
    print("""Functions usable are:
'abs'
'absolute'
'angle'
'sqrt'
'log'
'sin'
'sinh'
'arcsin'
'cos'
'cosh'
'arccos'
'tan'
'tanh'
'arctan'
""")
    print("Sawtooth wave form:")
    print("arctan(tan(x))")
    print("Triangle wave form:")
    print("arcsin(sin(x))")
    print("Type 'polar' to change to a circle graph")
    print("Type 'line' to change to a line graph")
    print("For further help, please look at the source code to figure it out,")
    print("Or, e-mail me at: alexpolosky@gmail.com")

def polarmenu(ran=frange(-100, 100, 0.01), once=False):
    if once != True:
        print("Function Plotter v2.0")
        print("~Hondros")
        print("Type in a function, or type 'help' for function commands")
        print("Type frange(x, y) for a specific x range)")
        print("Type set(radian) to convert list of numbers to radians (for sin)")
        print("Type show() to show the plot window")
        print("example: 2*sin(x)")
        print("")
    while True:
        try:
            f = raw_input("y = ")
            if f == 'help':
                menuhelp()
            if f[0:6] == 'frange':
                menu(eval(f), True)
            if f == 'set(radian)':
                menu(ranradians(ran), True)
            if f == 'show':
                show()
            if f == 'polar':
                polarmenu(ran, True)
            if f == 'line':
                menu(ran, True)
            else:
                y = funceval(f, ran)
                polar(y, ran)
        except:
            print("The function %s is invalid" %(f))

def menu(ran=frange(-100, 100, 0.01), once=False):
    if once != True:
        print("Function Plotter v2.0")
        print("~Hondros")
        print("Type in a function, or type 'help' for function commands")
        print("Type frange(x, y) for a specific x range)")
        print("Type set(radian) to convert list of numbers to radians (for sin)")
        print("Type show() to show the plot window")
        print("example: 2*sin(x)")
        print("")
    while True:
        try:
            f = raw_input("y = ")
            if f == 'help':
                menuhelp()
            if f[0:6] == 'frange':
                menu(eval(f), True)
            if f == 'set(radian)':
                menu(ranradians(ran), True)
            if f == 'show':
                show()
            if f == 'polar':
                polarmenu(ran, True)
            if f == 'line':
                menu(ran, True)
            else:
                y = funceval(f, ran)
                plot(ran, y)
        except:
            print("The function %s is invalid" %(f))

menu()

Stuff I want to work on:
1) Fix the (functions not valid) problem;
2) Change this whole thing into a class (simple enough);
3) Create a log of functions you make;
4) Show where the error was in your program