ValueError：在使用Sage绘图时“解压缩的值太多”

Question

here's my code thus far. I have Python 2.7 (which I downloaded today along with Sage) and am running it on Mac OS X 10.6.8 from the terminal (though, I do plan on running it from the notebook() GUI as soon as I figure out what's going on with these errors).

sage: import scipy
sage: import numpy
sage: import matplotlib
sage: cd /Users/nickscomputer/Desktop
/Users/nickscomputer/Desktop
sage: DATA = numpy.loadtxt("PracticeDat.txt")
sage: DATA
array([[   1.,    1.],
   [   2.,    4.],
   [   3.,    9.],
   [   4.,   16.],
   [   5.,   25.],
   [   6.,   36.],
   [   7.,   49.],
   [   8.,   64.],
   [   9.,   81.],
   [  10.,  100.]])
sage: X = DATA[:,0]
sage: Y = DATA[:,1]
sage: plot(X,Y)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)

/Users/nickscomputer/Desktop/<ipython console> in <module>()

/Applications/sage/local/lib/python2.7/site-packages/sage/misc/decorators.pyc in wrapper(*args, **kwds)
    685                     kwds[new_name] = kwds[old_name]
    686                     del kwds[old_name]
--> 687             return func(*args, **kwds)
    688         
    689         return wrapper

 /Applications/sage/local/lib/python2.7/site-packages/sage/misc/decorators.pyc in wrapper(*args, **kwds)
    532                 options['__original_opts'] = kwds
    533             options.update(kwds)
--> 534             return func(*args, **options)
    535 
    536         #Add the options specified by @options to the signature of the wrapped

/Applications/sage/local/lib/python2.7/site-packages/sage/plot/plot.pyc in plot(funcs, *args, **kwds)
   1024         # if there is one extra arg, then it had better be a tuple
   1025         elif n == 1:
-> 1026             G = _plot(funcs, *args, **kwds)
   1027         elif n == 2:
   1028         # if there are two extra args, then pull them out and pass them as a tuple

/Applications/sage/local/lib/python2.7/site-packages/sage/plot/plot.pyc in _plot(funcs, xrange,     parametric, polar, fill, label, randomize, **options)
   1095         return Graphics()
   1096     funcs, ranges = setup_for_eval_on_grid(funcs, [xrange], options['plot_points'])
-> 1097     xmin, xmax, delta = ranges[0]
   1098     xrange=ranges[0][:2]
   1099     #parametric_plot will be a list or tuple of two functions (f,g)

ValueError: too many values to unpack

I've tried doing a list_plot, and I get this error:

sage: list_plot(X,Y)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)

/Users/nickscomputer/Desktop/<ipython console> in <module>()

/Applications/sage/local/lib/python2.7/site-packages/sage/misc/decorators.pyc in wrapper(*args, **kwds)
    532                 options['__original_opts'] = kwds
    533             options.update(kwds)
--> 534             return func(*args, **options)
    535 
    536         #Add the options specified by @options to the signature of the wrapped

/Applications/sage/local/lib/python2.7/site-packages/sage/plot/plot.pyc in list_plot(data, plotjoined, **kwargs)
   1561     """
   1562     from sage.plot.all import line, point
-> 1563     if data == {} or data == () or data == []:
   1564         return Graphics()
   1565     if isinstance(data, dict):

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

I've also tried this option, which generates empty plot axes and this error:

sage: plot((X,Y))
verbose 0 (1978: plot.py, generate_plot_points) WARNING: When plotting, failed to evaluate  function at 200 points.
verbose 0 (1978: plot.py, generate_plot_points) Last error message: ''numpy.ndarray' object is not callable'
verbose 0 (1978: plot.py, generate_plot_points) WARNING: When plotting, failed to evaluate function at 200 points.
verbose 0 (1978: plot.py, generate_plot_points) Last error message: ''numpy.ndarray' object is not callable'

Answer 1

Use list_plot . Its documentation says

If you have separate lists of x values and y values which you want to plot against each other, use the "zip" command to make a single list whose entries are pairs of (x,y) values, and feed the result into "list_plot"

so in particular, use list_plot(zip(X,Y)) . Alternatively, convert DATA to a single list: use list_plot(DATA.tolist()) .

Answer 2

I'd also point out that I like using line() with the linestyle='' option so I can get more matplotlib options (for some reason list_plot and points don't do this nicely):

DATA = [[   1.,    1.],
   [   2.,    4.],
   [   3.,    9.],
   [   4.,   16.],
   [   5.,   25.],
   [   6.,   36.],
   [   7.,   49.],
   [   8.,   64.],
   [   9.,   81.],
   [  10.,  100.]]
line(DATA,marker='^',linestyle='')