python: Multiple plotting in one subplot2grid-image
Question: Let f be a function that depends on an independent variable x and on one (or
more) parameter b. My goal is to draw f for several values of b into the same
image. And I want that b is a global value (so that I can quickly change it).
Consider the code

    
    
    import numpy as np
    import pylab as pl
    
    b=0.5
    def f(x,b):
        return np.sin(x*b)*b
    
    X = np.linspace(0,10,1000)
    F = f(X,b)
    pl.figure(figsize=(12, 16), num="My sine")
    pl.plot(X, F, label='b = %f' %b)
    pl.legend(loc="best")
    

This code can be evaluated multiple times, just with another value for b. Then
all the curves are drawn into the same figure.

Now the problem: If in the above code I put

    
    
    pl.subplot2grid((4, 1), (0, 0), rowspan=3)
    

between `pl.plot` and `pl.legend`, every new evaluation of the code is drawn
into a new blank figure.

So, how can I realise that with using `pl.subplot2grid` each evaluation is
drawn into the same figure?


Answer: Maybe you are looking for something like this?:

    
    
    import numpy as np
    import pylab as pl
    
    def f(x,b):
        return np.sin(x*b)*b
    
    def draw(b):
        X = np.linspace(0,10,1000)
        F = f(X,b)
        ax1.plot(X, F, label='b = %f' %b)
    
    
    # Main program
    fig = pl.figure(figsize=(12, 16), num="My sine")
    ax1 = pl.subplot2grid((4,3), (0,0), colspan=2)
    
    for b in [0.4, 0.5, 0.6]:
        draw(b)
    
    pl.legend(loc="best")
    pl.show()
    

[![enter image description
here](http://i.stack.imgur.com/HYAEl.png)](http://i.stack.imgur.com/HYAEl.png)

