WCS作为使用astropy加载的datacube切片的matplotlib投影？

Question

我有一个名为“我的”的FITS文件_立方体拟合'与WCS。该文件包含轴1和轴2（X和Y）的空间信息和轴3（Z）的光谱信息。当我用astropy.io.适合，谱轴为0，空间轴为1和2。文件的加载方式如下：

    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WCS显示数据立方体的单个光谱帧。比如说：

^{pr2}$

如果我这么做，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，因为您用完整的标题初始化了它（我假设您的头也包含一个光谱WCS解决方案）。因此，仅使用空间创建二维绘图是行不通的，因为给子图的投影是三维的

我自己没有这样做，也没有一个示例文件，但是WCS文档提到可以使用the sub function, or even the celestial functions来获取单个轴或天体（空间）轴；这些函数将返回一个只包含这些轴的WCS对象。在

因此，您可以使用以下方法：

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