Passing string as an argument for plotting

Question

I would like this function to take a string, indicating which data(x, y or z) it should plot, as an argument.

def plotfit(axis):

    fig = plt.figure()
    ax = fig.gca(projection='3d')
    ax.set_xlabel('x')
    ax.set_ylabel('y')
    ax.set_zlabel('z')
    ax.scatter(xdata, ydata, func_z(vars,fitted_z),c='r')
    ax.set_title('B_z of %s' % name)
    ax.scatter(xdata, ydata, zfield, c='b')

How do I make the bolded parts of the code below replaced by my string argument so that, e.g. plotfit(x) would replace all instances of bolded z below with "x" and plot accordingly ? Points of interest:

func_z
fitted_z
zfield
'B_z of %s'

What I imagine would be something along the lines of:

ax.scatter(xdata, ydata, func(axis as a string)(vars,fitted_(axis as a string)),c='r')

`def plotfit()` doesn't take any input arguments. Can you please elaborate a little bit more on what exactly it is you want to do? Do you want to add arguments to it? — rbaleksandar, Feb 08 '16 at 12:51
Could you edit the question to include some examples of how your are hoping to call this function? — Martin Evans, Feb 08 '16 at 12:55
@joo I think my solution solves the issue, if not please let me know. — Rob Murray, Feb 08 '16 at 13:06

kernel_panic · Answer 1 · 2016-02-08T13:28:43.177

You can use a dictionary that will act as a switch statement in your code as outlined below.

def plotfit(a_letter):
    assert a_letter in ["x", "y", "z"]
    fitted = {"x" : fitted_x, "y" : fitted_y, "z" : fitted_z}
    fields = {"x" : field_x, "y" : field_y, "z" : field_z}
    afunc = {"x" : afunc_x, "y" : afunc_y, "z" : afunc_z}
    # ...
    ax.scatter(xdata, ydata, afunc[a_letter](vars,fitted[a_letter]),c='r')
    #...
    ax.set_title('B_%s of %s' %(a_letter, name))

However, you could also consider the alternatives:

Have plotfit to take the functions fitted, func, field as argument
Have plotfit to take an object as argument that would have the fitted ,func and field methods
Have plotfit defined in a base class and uses self.func, self.fit and self.field. Those methods would be implemented in different subclasses

Note that using exec statement for such a case is seen as bad practice as described in Why should exec() and eval() be avoided?

score 0 · Accepted Answer · edited May 23 '17 at 12:15

0

One solution is to use exec to execute different code depending on the string type argument I presume you want to parse to the function, for example:

def plotfit(axis):
    fig = plt.figure()
    ax = fig.gca(projection='3d')
    ax.set_xlabel('x')
    ax.set_ylabel('y')
    ax.set_zlabel('z')
    exec("ax.scatter(xdata, ydata, func_" + axis + "(vars,fitted_" + axis + "),c='r')")

A similar technique can be used for the other lines you want to do this on.

Please bear in mind that it is not recommended to use exec (or eval) as it can often hide bugs and can be ambiguous. See: Why should exec() and eval() be avoided?

edited May 23 '17 at 12:15

Community

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answered Feb 08 '16 at 13:02

Rob Murray

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Worked as expected, thank you. I am not allowed to edit your post, there is one missing closing parenthesis. – joo Feb 08 '16 at 13:16
The end should look like this: c='r')") – joo Feb 08 '16 at 15:06

Passing string as an argument for plotting

2 Answers2