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import - How to read CDF (Common Data Format) file?


I don't understand, what Import does with CDF.


If I enter



In[17]:= data = Import[ExampleFile]
Out[17]= {"Pose"}

what I can do with returned object? How can I return Pose entry only?


If I try to specify this as element name as string, I am failing:


In[18]:= data = Import[ExampleFile, "Pose"]

During evaluation of In[18]:= Import::noelem: The Import element "Pose" is not present when importing as NASACDF.

Out[18]= $Failed


UPDATE


I noticed, that it showed entity name in quotes. In notebook it looks different:


enter image description here


i.e. w/o quotes.


UDPATE 2


Shared example: https://drive.google.com/open?id=0By8pZ9a2478YOGlhZUlRU3VNb28


UPDATE 3


Apparently Mathematica has a bug here, because the data returned is reshaped incorrectly.


Here is Matlab transcript, reading the same file:



>> data = cdfread(ExampleFile,'Variable', {'Pose'});
>> data = data{1};
>> size(data)

ans =

   992    96

>> data(1,1:5)


ans =

  1×5 single row vector

 -287.2470   64.5002  933.7140 -417.2063   37.0789

>> data(1:5,1)

ans =


  5×1 single column vector

 -287.2470
 -287.6960
 -288.1260
 -288.5740
 -288.9960

An here is Mathematicas:


In[47]:= data = Import[ExampleFile, "Elements"]

data = Import[ExampleFile, "Data"];
Dimensions[data]
data[[1, 1, 1, 1]]

Out[47]= {"Annotations", "Data", "DataEncoding", "DataFormat", \
"Datasets", "Metadata"}

Out[49]= {1, 1, 992, 96}

Out[50]= -287.247


data[[1, 1, 1, Range[5]]]

Out[54]= {-287.247, -287.696, -288.126, -288.574, -288.996}

In[55]:= data[[1, 1, Range[5], 1]]

Out[55]= {-287.247, -497.341, -378.209, -376.513, -370.388}

I.e. although Mathematica indicates the similar shape of data, i.t. fills that shape in different way.



I.e. what Matlab cosiders as row, Mathematica considers as column, and what Mathematica considers as column, is unknown.


So, I still need instructions if I am incorrectly operating with Mathematica's ND arrays, or, if it is Mathematica bug, I need to know, how to recover from it.


UPDATE 4


For now I see the following way to recover original data from corrupted one:


dims = Dimensions[data]
data = ArrayReshape[
   data, {dims[[1]], dims[[2]], dims[[4]], dims[[3]]}];
data = Transpose[data, {1, 2, 4, 3}];

Answer



In WL this format is known as NASACDF



In doubt you can always import "Elements" and try each one:


Import["Posing.cdf", "Elements"]


{"Annotations", "Data", "DataEncoding", "DataFormat", "Datasets", "Metadata"}

Import["Posing.cdf", "Data"]

enter image description here


Initially returned {"Pose"} was a list of datasets stored in a file. You can extract specific dataset via:



 Import["Posing.cdf", {"Datasets", "Pose"}]

All that and more can of course be learned from linked documentation page.


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