IRISPy and NDCube

2017-08-29T00:00:00+00:00

GSoC has come to an end, it was one of the best summer experience I had. In this summer I had to create a new affiliated package IRISPy but during this project making a base package for multi-dimensional contiguous and non-contiguous spatially aware arrays (from readme.md of NDCube) was a natural step so ended up developing another repository NDCube. This was initially a part of sunpycube but after breaking and burning everything we ended up with ndcube :P.

NDCube

NDCube.

PR10.

The NDCube has two container objects:

1. NDCube which can handle n-dimensional data containing WCS objects and metadata. This has different methods such as:

The basic slicing i.e __getitem__ of N-dimensional objects like numpy.array and this also handle the slicing of WCS objects. Suppose we are dropping a axis, this is handled by setting the WCS value to one for that axis.

In [4]: cube2.dimensions
Out[4]: DimensionPair(shape=<Quantity [ 2., 3., 4.] pix>, axis_types=['HPLN-TAN', 'HPLT-TAN', 'WAVE'])
In [5]: cube2
Out[5]:
Sunpy NDCube
---------------------
WCS Keywords
Number of WCS axes: 3
CTYPE : 'WAVE'  'HPLT-TAN'  'HPLN-TAN'
CRVAL : 1.0000000000000001e-09  0.5  1.0
CRPIX : 0.0  2.0  2.0
PC1_1 PC1_2 PC1_3  : 1.0  0.0  0.0
PC2_1 PC2_2 PC2_3  : 0.0  1.0  0.0
PC3_1 PC3_2 PC3_3  : 0.0  0.0  1.0
CDELT : 2.0000000000000002e-11  0.5  0.40000000000000002
NAXIS : 4  3  2
---------------------
Length of NDCube: [ 2.  3.  4.] pix
Axis Types of NDCube: ['HPLN-TAN', 'HPLT-TAN', 'WAVE']
In [6]: cube2[0, :, :]
Out[6]:
Sunpy NDCube
---------------------
WCS Keywords
Number of WCS axes: 3
CTYPE : 'WAVE'  'HPLT-TAN'  'HPLN-TAN'
CRVAL : 1.0000000000000001e-09  0.5  1.0
CRPIX : 0.0  2.0  2.0
PC1_1 PC1_2 PC1_3  : 1.0  0.0  0.0
PC2_1 PC2_2 PC2_3  : 0.0  1.0  0.0
PC3_1 PC3_2 PC3_3  : 0.0  0.0  1.0
CDELT : 2.0000000000000002e-11  0.5  0.40000000000000002
NAXIS : 4  3  1
---------------------
Length of NDCube: [ 3.  4.] pix
Axis Types of NDCube: ['HPLT-TAN', 'WAVE']
In [7]: cube2[0, :, :].dimensions
Out[7]: DimensionPair(shape=<Quantity [ 3., 4.] pix>, axis_types=['HPLT-TAN', 'WAVE'])

plot() method that animates if dimension is greater than 2, else if dimension less than equal to 2 than plots images, this animations uses the WCS data for the axis.

world_to_pixel() method converts world coordinates to pixel coordinates, this method is unit aware.

pixel_to_world() method converts pixel coordinates to world coordinates, this method is unit aware.

to_sunpy() this method automates the conversion of present NDCube instance to sunpy instance is it satisfies all the necessary requirements. Presently it supports Map and work is going on in TimeSeries.

2. NDCubeSequence which handles a list of NDCube object, this also handles extra coordinate axis which is parallel to one of the data axis. This has methods such as:

plot() method that creates a animation using the data of the WCS for the axis.

__getitem__ method that slices the sequence like a list containing NDCubes which also handles slicing of WCS objects.

index_as_cube() this method handles the slicing of sequence as a single N-dimensional object. Example: if the dimension of NDCube objects inside the list of NDCubeSequence is 3 then this method will treat slicing of sequence as single 3 dimensional object by concatenating all the cubes. So this makes the dimensions as (len(list_inside_cubesequence)*NDCube[1st dimension], NDCube[2nd dimension], NDCube[3rd dimension]).

explode_along_axis() method that slices NDCube object along that axis. This is useful to reduce the dimension of NDCube’s inside the sequence list. This will create a new sequence as this break the cube along one axis.

to_sunpy() method it creates a new Sunpy instance if it satisfies the requirements. Presently only mapcube is implemented.

IRISPy

PR3.

IRISPy class was a easy implementation after the useful and challenging NDCube repository was alive. This made creating a new class such as IRISSpectrograph a rather simple task. This was done in a clean and neat way.

So this class object has all the inherent methods and properties of NDCubeSequence as it uses this as it’s base class.

Future work includes making changes to IRISSpectrograph to include the recently added changes such as SpectrographSequence, so this is a new sequence which is using the NDCubeSequence as it’s parent class. Making the iris tools working properly with the new IRISSpectrograph. Developing NDCube’s and NDCubeSequence’s to_sunpy method to handle all the sunpy objects.

Blog - Posts by Ankit Baruah

IRISPy and NDCube

NDCube

IRISPy