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POnumpy append_field gives shape error for new field with 2d shape
 

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  1. POnumpy append_field gives shape error for new field with 2d shape
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    <p>I have a structured numpy array, I want to use the recfunctions library <a href="http://pyopengl.sourceforge.net/pydoc/numpy.lib.recfunctions.html" rel="nofollow noreferrer">http://pyopengl.sourceforge.net/pydoc/numpy.lib.recfunctions.html</a> function append_fields() or rec_append_fields() to append a field with some shape to it. However, I get an error:</p> <blockquote> <p>ValueError: operands could not be broadcast together with shapes (10) (10,3) </p> </blockquote> <p>where <code>10</code> is the length of my existing array, and <code>(3,)</code> is the shape of the field I want to append.</p> <p>For example:</p> <pre><code>import numpy as np from numpy.lib.recfunctions import append_fields my_structured_array = np.array( zip([0,1,2,3],[[4.3,3.2],[1.4,5.6],[6.,2.5],[4.5,5.4]]), dtype=[('id','int8'),('pos','2float16')] ) my_new_field = np.ones( len(my_structured_array), dtype='2int8' ) my_appended_array = append_fields( my_structured_array, 'new', data=my_new_field ) </code></pre> <blockquote> <p>ValueError: operands could not be broadcast together with shapes (4) (4,2) </p> </blockquote> <p>Any ideas? I tried making <code>my_new_field</code> a list of tuples and putting a dtype argument with the proper shape into the append_fields():</p> <pre><code>my_new_field = len(my_structured_array)*[(1,1)] my_appended_array = append_fields( my_structured_array, 'new', data=my_new_field, dtype='2int8' ) </code></pre> <p>but that seems to end up the same once it gets converted to a numpy array.</p> <p>None of this seems to change when I use rec_append_fields() instead of simply append_fields()</p> <p>EDIT: In light of the fact that my new field doesn't have the same shape as my array, I suppose that my desired append is impossible, suggested by <a href="https://stackoverflow.com/users/895755/radicalbiscuit">@radicalbiscuit</a>.</p> <pre><code>In : my_new_field.shape Out: (4, 2) In : my_structured_array.shape Out: (4,) </code></pre> <p>But, I included one of the original fields in the array with shape different from the original array to make my point, which is that a field does not have to have the same shape as the structured array. How can I append a field like this?</p> <pre><code>In : my_structured_array['pos'].shape Out: (4, 2) In : my_new_field.shape Out: (4, 2) </code></pre> <p>I should note that for my application, I can append an empty field as long as it's possible to somehow change the shape later. Thanks!</p>
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