WCS作为使用astropy加载的数据立方体切片的matplotlib投影？

Question

我有一个名为'my_cube.fits'的FITS文件,带有WCS.该文件具有关于轴1和2(X和Y)的空间信息以及关于轴3(Z)的光谱信息.当我使用astropy.io.fits加载它时,谱轴为0,空间轴为1和2.文件加载如下:

    import astropy.io.fits as pyfits

    filename = 'my_cube.fits'
    my_data = pyfits.getdata(filename)
    my_header = pyfits.getheader(filename)

我一直在使用matplotlib来显示数据,我想知道如何使用它的WCS显示我的数据立方体的单个光谱帧.让我们说:

    from astropy.wcs import WCS
    from matplotlib import pyplot as plt

    my_wcs = WCS(my_header)
    fig = plt.figure()
    ax = fig.add_subplot(111, projection=my_wcs)
    ax.imshow(my_data[5, :, :])

    plt.show()

如果我这样做,我有:

    ...
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/figure.py", line 1005, in add_subplot
    a = subplot_class_factory(projection_class)(self, *args, **kwargs)
    File "/usr/local/lib/python3.4/dist-packages/matplotlib/axes/_subplots.py", line 73, in __init__
    self._axes_class.__init__(self, fig, self.figbox, **kwargs)
    File "/usr/local/lib/python3.4/dist-packages/wcsaxes/core.py", line 49, in __init__
    self.patch = self.coords.frame.patch
    File "/usr/local/lib/python3.4/dist-packages/wcsaxes/frame.py", line 129, in patch
    self._update_patch_path()
    File "/usr/local/lib/python3.4/dist-packages/wcsaxes/frame.py", line 115, in _update_patch_path
    self.update_spines()
    File "/usr/local/lib/python3.4/dist-packages/wcsaxes/frame.py", line 192, in update_spines
    self['b'].data = np.array(([xmin, ymin], [xmax, ymin]))
    File "/usr/local/lib/python3.4/dist-packages/wcsaxes/frame.py", line 40, in data
    self._world = self.transform.transform(self._data)
    File "/usr/local/lib/python3.4/dist-packages/wcsaxes/transforms.py", line 166, in transform
    world = self.wcs.wcs_pix2world(pixel_full, 1)
    File "/usr/local/lib/python3.4/dist-packages/astropy/wcs/wcs.py", line 1329, in wcs_pix2world
'output', *args, **kwargs)
    File "/usr/local/lib/python3.4/dist-packages/astropy/wcs/wcs.py", line 1231, in _array_converter
    return _return_single_array(xy, origin)
    File "/usr/local/lib/python3.4/dist-packages/astropy/wcs/wcs.py", line 1212, in _return_single_array
"of shape (N, {0})".format(self.naxis))
    ValueError: When providing two arguments, the array must be of shape (N, 3)

Answer 1

您的WCS对象包含两个空间轴和光谱轴,因为您使用完整标题初始化它(我假设您的标题还包含光谱WCS解决方案).因此,仅使用空间创建2D绘图将不起作用,因为您对子绘图的投影是3D.

我自己没有这样做,也没有示例文件,但是WCS文档提到你可以使用子函数,甚至是天体函数来获得各个轴或天体(空间)轴; 这些函数将只返回那些轴的WCS对象.

因此,您可以使用以下内容:

my_wcs = WCS(my_header).celestial
fig = plt.figure()
ax = fig.add_subplot(111, projection=my_wcs)