Plotting functions using csplot.py

There is a set of functions in the file csplot.py with which you can create plots of data. You can download csplot.py to your computer by right-clicking (Windows) or control-clicking (Mac) the link below and choosing to save the file:

Download csplot.py from this link.

You need to make sure that csplot.py and hw2pr1.py are placed in the same directory.

In your IDLE editing window, add the following line to your hw2pr1.py file:

from csplot import *

This line above will make all of the functions in csplot.py available to you in IDLE's shell after you press F5.

As a first graphical plot, we will create a parabola. First, in your hw2pr1.py file, copy this squaring function:

def sq(x):

""" sq(x) squares its input

input: x, a numeric value

"""

return x**2

Save your hw2pr1.py file and press F5 to load it into the Shell. At the Python prompt, try the following example using your fsteps function:

>>> Y = fsteps(sq,-2,2,128)

>>> Y

(you'll see the 128 values in the list Y)

>>> plot(Y,-2,2)

You should see a window with a happy parabola, e.g.,

If you don't see a window, it might be "hiding" behind the rest of your windows, so look around for it.

You'll notice that after the plot window opens, you can no longer type commands into Python's shell. To gain control and enter more commands, you need to close the window containing the plot. Go ahead and close this window now.

After closing the window, return the Shell and try the following:

>>> Y = fsteps(math.cos, 0, 20, 200)

>>> plot(Y,0,20)

A window should come up that looks somewhat pythonic:

Close this window again to get control back to the shell.

For a view of the rectangles that will contribute to the integral of the function, try the following:

>>> Y = fsteps(math.cos, 0, 20, 200)

>>> plot(Y,0,20,'sprecL')

How can I change the plot window?

Here is a brief list of functions you can use.

1. plot(Y,low,hi) plots line segments joining the data in the list Y evenly spaced from low to hi (excluding hi). It is also available as plotS(Y,low,hi).

2. plot(Y,low,hi,'p') plots only the points in Y, not the line segments connecting them.

3. plot(Y,low,hi,'recL') plots rectangles with their upper-Left-hand vertices in Y.

For convenience, you can concatenate the strings that are the optional fourth parameter, with 's' representing the default line-segment plot. Thus, plot(Y,low,hi,'sprecL') gives you the "spreckle" plot with lots of goodies.

csplot documentation contains more detailed descriptions of the functions and fourth parameter options - you will not need these, however!

Here are some keyboard-and-mouse actions:

1. shift-mousedrag zooms the canvas in/out as you go toward/away from the center

2. z-mousedrag zooms the canvas in centered on the rectangle defined by the cursor

3. x-mousedrag zooms only the horizontal axis

4. y-mousedrag zooms only the vertical axis

5. t-mousedrag translates or slides the canvas around

6. p-left click (clicking with the 'p' key pressed) prints the position of the mouse both in terms of pixels on the screen and the plot

7. ctrl-left click centers the canvas at the clicked position

8. R resets the zoom and centers the view

9. ? displays csplot Help

Once you understand how to use csplot, return to Lab2 and continue working.