I have a record array r and I want to add a new field to it. I have been looking at setfield but I am not sure how to use it for this purpose. Eg
# r is some npy record array N = len(r) x = npy.zeros(N) # add array of floats x to r with dtype name 'jdh' and type '<f8'
Any suggestions?
JDH
John Hunter wrote:
I have a record array r and I want to add a new field to it. I have been looking at setfield but I am not sure how to use it for this purpose. Eg
# r is some npy record array N = len(r) x = npy.zeros(N) # add array of floats x to r with dtype name 'jdh' and type '<f8'
Any suggestions?
Here is the straightforward way:
In [15]: import numpy as np
In [16]: dt = np.dtype([('foo', int), ('bar', float)])
In [17]: r = np.zeros((3,3), dtype=dt)
In [18]: r Out[18]: array([[(0, 0.0), (0, 0.0), (0, 0.0)], [(0, 0.0), (0, 0.0), (0, 0.0)], [(0, 0.0), (0, 0.0), (0, 0.0)]], dtype=[('foo', '<i4'), ('bar', '<f8')])
In [19]: def append_field(rec, name, arr, dtype=None): arr = np.asarray(arr) if dtype is None: dtype = arr.dtype newdtype = np.dtype(rec.dtype.descr + [(name, dtype)]) newrec = np.empty(rec.shape, dtype=newdtype) for field in rec.dtype.fields: newrec[field] = rec[field] newrec[name] = arr return newrec ....:
In [29]: append_field(r, 'jdh', ones((3,3))) Out[29]: array([[(0, 0.0, 1.0), (0, 0.0, 1.0), (0, 0.0, 1.0)], [(0, 0.0, 1.0), (0, 0.0, 1.0), (0, 0.0, 1.0)], [(0, 0.0, 1.0), (0, 0.0, 1.0), (0, 0.0, 1.0)]], dtype=[('foo', '<i4'), ('bar', '<f8'), ('jdh', '<f8')])
On 9/26/07, Robert Kern robert.kern@gmail.com wrote:
Here is the straightforward way:
In [15]: import numpy as np
In [16]: dt = np.dtype([('foo', int), ('bar', float)])
In [17]: r = np.zeros((3,3), dtype=dt)
Here is a (hopefully) simple question. If I create an array like this, how can I efficiently convert it to a record array which lets me do r.attr in addition to r['attr']. I'm pretty addicted to the former syntax.
In [114]: dt = np.dtype([('foo', int), ('bar', float)])
In [115]: r = np.zeros((3,3), dtype=dt)
In [116]: r.dtype Out[116]: dtype([('foo', '<i4'), ('bar', '<f8')])
In [117]: r['foo'] Out[117]: array([[0, 0, 0], [0, 0, 0], [0, 0, 0]])
In [118]: r.foo ------------------------------------------------------------ Traceback (most recent call last): File "<ipython console>", line 1, in ? AttributeError: 'numpy.ndarray' object has no attribute 'foo'
Thanks, JDH
Try
r = r.view(numpy.recarray)
barry
On 10/5/07, John Hunter jdh2358@gmail.com wrote:
On 9/26/07, Robert Kern robert.kern@gmail.com wrote:
Here is the straightforward way:
In [15]: import numpy as np
In [16]: dt = np.dtype([('foo', int), ('bar', float)])
In [17]: r = np.zeros((3,3), dtype=dt)
Here is a (hopefully) simple question. If I create an array like this, how can I efficiently convert it to a record array which lets me do r.attr in addition to r['attr']. I'm pretty addicted to the former syntax.
In [114]: dt = np.dtype([('foo', int), ('bar', float)])
In [115]: r = np.zeros((3,3), dtype=dt)
In [116]: r.dtype Out[116]: dtype([('foo', '<i4'), ('bar', '<f8')])
In [117]: r['foo'] Out[117]: array([[0, 0, 0], [0, 0, 0], [0, 0, 0]])
In [118]: r.foo
Traceback (most recent call last): File "<ipython console>", line 1, in ? AttributeError: 'numpy.ndarray' object has no attribute 'foo'
Thanks, JDH _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
John Hunter wrote:
On 9/26/07, Robert Kern robert.kern@gmail.com wrote:
Here is the straightforward way:
In [15]: import numpy as np
In [16]: dt = np.dtype([('foo', int), ('bar', float)])
In [17]: r = np.zeros((3,3), dtype=dt)
Here is a (hopefully) simple question. If I create an array like this, how can I efficiently convert it to a record array which lets me do r.attr in addition to r['attr']. I'm pretty addicted to the former syntax.
In [32]: r2 = r.view(np.recarray)
In [33]: r2.foo Out[33]: array([[0, 0, 0], [0, 0, 0], [0, 0, 0]])
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Barry Wark -
John Hunter -
Robert Kern