Write a program to draw a text-based graph of a mathematical function f(x). Use

Question

Write a program to draw a text-based graph of a mathematical function f(x). Use axis limits of -10 to 10 and only plot discrete points i.e. points with integer value ordinates.

Sample I/O:

Enter a function f(x):

x+2

please see picture

Use nested loops to print the entire area of the graph (i.e. an outer loop for rows and an inner one for columns), keeping track of the current x and y values. Whenever the (rounded) value of the function f(x), entered by the user, is equal to the current y value, output "o" (small letter Oh), otherwise, output either the appropriate axis character or a space.

NOTE: Remember to import math to enable the use of some mathematical functions. How should the program support the entering of arbitrary functions?

? Obtain user input in the form of a string, then within the inner loop,

? whenever f(x) is to be calculated, use the Python

Explanation / Answer

Code

#!/usr/bin/env python2

"""

grph.py

"""

#_____________________________________________________________________________

# Imports

#

from math import sin, cos, tan

import os

import sys

#_____________________________________________________________________________

# Functions

#

def fprintf(fstream, fmt, *args):

"""

Emulate C's fprintf() function.

"""

fmt %= args

fstream.write(fmt)

return len(fmt)

def plot(x_expression, xmin, xmax, ymin, ymax):

"""

plot(str, int, int, int, int) -> str

Return a string representation of a graph of x_expression.

BUGS:

- The graph is inverted.

- Zero Divison Error when expressions like `1/x` are passed as

x_expression.

"""

return ' '.join(

''.join((

lambda x,y: 'o' if round(eval(x_expression)) == y else (

' ' if y != 0 and x != 0 else (

'|' if y != 0 and x == 0 else (

'-' if y == 0 and x != 0 else

'+' ))))

(x,y)

for x in xrange(xmax, xmin-1, -1))

for y in xrange(ymax, ymin-1, -1))

#_____________________________________________________________________________

# Main function

#

def main():

x_expression = raw_input("f(x) = ")

fprintf(sys.stdout, " Graph of f(x) = %s %s ",

x_expression,

plot(x_expression, -10, 10, -10, 10))

return 0

if __name__ == '__main__':

main()

# =================

Sample Test case:

stdin

copy

stdout

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