Another masked array question
Hello, Consider my masked arrays: I[28]: type basic.data['Air_Temp'] > type(basic.data['Air_Temp']) O[28]: numpy.ma.core.MaskedArray I[29]: basic.data['Air_Temp'] O[29]: masked_array(data = [   ...,   ], mask = [ True True True ..., True True True], fill_value = 999999.9999) I[17]: basic.data['Air_Temp'].data = np.ones(len(basic.data['Air_Temp']))*30  AttributeError Traceback (most recent call last) > 1 2 3 4 5 AttributeError: can't set attribute Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works: I[13]: basic.data['Air_Temp'].data[0] = 30 Shouldn't this be working like the regular NumPy arrays do? Thanks.  Gökhan
On Sat, May 8, 2010 at 7:52 PM, Gökhan Sever <gokhansever@gmail.com> wrote:
Hello,
Consider my masked arrays:
I[28]: type basic.data['Air_Temp'] > type(basic.data['Air_Temp']) O[28]: numpy.ma.core.MaskedArray
I[29]: basic.data['Air_Temp'] O[29]: masked_array(data = [   ...,   ], mask = [ True True True ..., True True True], fill_value = 999999.9999)
I[17]: basic.data['Air_Temp'].data = np.ones(len(basic.data['Air_Temp']))*30  AttributeError Traceback (most recent call last)
> 1 2 3 4 5
AttributeError: can't set attribute
Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works:
I[13]: basic.data['Air_Temp'].data[0] = 30
Shouldn't this be working like the regular NumPy arrays do?
Based on the traceback, I'd say it's because you're trying to replace the object pointed to by the .data attribute. Instead, try to just change the bits contained in .data: basic.data['Air_Temp'].data[:] = np.ones(len(basic.data['Air_Temp']))*30 Ryan  Ryan May Graduate Research Assistant School of Meteorology University of Oklahoma
On Sat, May 8, 2010 at 9:16 PM, Ryan May <rmay31@gmail.com> wrote:
On Sat, May 8, 2010 at 7:52 PM, Gökhan Sever <gokhansever@gmail.com> wrote:
Hello,
Consider my masked arrays:
I[28]: type basic.data['Air_Temp'] > type(basic.data['Air_Temp']) O[28]: numpy.ma.core.MaskedArray
I[29]: basic.data['Air_Temp'] O[29]: masked_array(data = [   ...,   ], mask = [ True True True ..., True True True], fill_value = 999999.9999)
I[17]: basic.data['Air_Temp'].data = np.ones(len(basic.data['Air_Temp']))*30

AttributeError Traceback (most recent call last)
> 1 2 3 4 5
AttributeError: can't set attribute
Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works:
I[13]: basic.data['Air_Temp'].data[0] = 30
Shouldn't this be working like the regular NumPy arrays do?
Based on the traceback, I'd say it's because you're trying to replace the object pointed to by the .data attribute. Instead, try to just change the bits contained in .data:
basic.data['Air_Temp'].data[:] = np.ones(len(basic.data['Air_Temp']))*30
Ryan
 Ryan May Graduate Research Assistant School of Meteorology University of Oklahoma
Thanks for the pointer Ryan. Now it works as it is supposed to be.  Gökhan
On 05/08/2010 04:16 PM, Ryan May wrote:
On Sat, May 8, 2010 at 7:52 PM, Gökhan Sever<gokhansever@gmail.com> wrote:
Hello,
Consider my masked arrays:
I[28]: type basic.data['Air_Temp'] > type(basic.data['Air_Temp']) O[28]: numpy.ma.core.MaskedArray
I[29]: basic.data['Air_Temp'] O[29]: masked_array(data = [   ...,   ], mask = [ True True True ..., True True True], fill_value = 999999.9999)
I[17]: basic.data['Air_Temp'].data = np.ones(len(basic.data['Air_Temp']))*30  AttributeError Traceback (most recent call last)
> 1 2 3 4 5
AttributeError: can't set attribute
Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works:
I[13]: basic.data['Air_Temp'].data[0] = 30
Shouldn't this be working like the regular NumPy arrays do?
Based on the traceback, I'd say it's because you're trying to replace the object pointed to by the .data attribute. Instead, try to just change the bits contained in .data:
basic.data['Air_Temp'].data[:] = np.ones(len(basic.data['Air_Temp']))*30
Also, you since you are setting all elements to a single value, you don't need to generate an array on the righthand side. And, you don't need to manipulate ".data" directlyI think it is best to avoid doing so. Consider: In [1]:x = np.ma.array([1,2,3], mask=[True, True, True], dtype=float) In [2]:x Out[2]: masked_array(data = [  ], mask = [ True True True], fill_value = 1e+20) In [3]:x[:] = 30 In [4]:x Out[4]: masked_array(data = [30.0 30.0 30.0], mask = [False False False], fill_value = 1e+20) In [5]:x[:] = np.ma.masked In [6]:x Out[6]: masked_array(data = [  ], mask = [ True True True], fill_value = 1e+20) In [7]:x.data Out[7]:array([ 30., 30., 30.]) Eric
Ryan
On Sat, May 8, 2010 at 9:29 PM, Eric Firing <efiring@hawaii.edu> wrote:
On 05/08/2010 04:16 PM, Ryan May wrote:
On Sat, May 8, 2010 at 7:52 PM, Gökhan Sever<gokhansever@gmail.com> wrote:
Hello,
Consider my masked arrays:
I[28]: type basic.data['Air_Temp'] > type(basic.data['Air_Temp']) O[28]: numpy.ma.core.MaskedArray
I[29]: basic.data['Air_Temp'] O[29]: masked_array(data = [   ...,   ], mask = [ True True True ..., True True True], fill_value = 999999.9999)
I[17]: basic.data['Air_Temp'].data = np.ones(len(basic.data['Air_Temp']))*30
AttributeError Traceback (most recent call last)
> 1 2 3 4 5
AttributeError: can't set attribute
Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works:
I[13]: basic.data['Air_Temp'].data[0] = 30
Shouldn't this be working like the regular NumPy arrays do?
Based on the traceback, I'd say it's because you're trying to replace the object pointed to by the .data attribute. Instead, try to just change the bits contained in .data:
basic.data['Air_Temp'].data[:] = np.ones(len(basic.data['Air_Temp']))*30
Also, you since you are setting all elements to a single value, you don't need to generate an array on the righthand side. And, you don't need to manipulate ".data" directlyI think it is best to avoid doing so. Consider:
In [1]:x = np.ma.array([1,2,3], mask=[True, True, True], dtype=float)
In [2]:x Out[2]: masked_array(data = [  ], mask = [ True True True], fill_value = 1e+20)
In [3]:x[:] = 30
In [4]:x Out[4]: masked_array(data = [30.0 30.0 30.0], mask = [False False False], fill_value = 1e+20)
In [5]:x[:] = np.ma.masked
In [6]:x Out[6]: masked_array(data = [  ], mask = [ True True True], fill_value = 1e+20)
In [7]:x.data Out[7]:array([ 30., 30., 30.])
Eric
Ryan
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Good to see this :) I[45]: x = np.ma.array([1,2,3], mask=[True, True, True], dtype=float) I[46]: x O[46]: masked_array(data = [  ], mask = [ True True True], fill_value = 1e+20) I[47]: x.data[:] = 25 I[48]: x O[48]: masked_array(data = [  ], mask = [ True True True], fill_value = 1e+20) I[49]: x[:] = 25 I[50]: x O[50]: masked_array(data = [25.0 25.0 25.0], mask = [False False False], fill_value = 1e+20) I was also updating mask values after updating data attribute. Now setting the masked array itself to a number automatically flips the masks for me which is very useful. I check if a valid temperature exists, otherwise assign my calculation to another missing value.  Gökhan
On May 8, 2010, at 9:51 PM, Gökhan Sever wrote:
On Sat, May 8, 2010 at 9:29 PM, Eric Firing <efiring@hawaii.edu> wrote: On 05/08/2010 04:16 PM, Ryan May wrote:
On Sat, May 8, 2010 at 7:52 PM, Gökhan Sever<gokhansever@gmail.com> wrote:
AttributeError: can't set attribute
Why this assignment fails? I want to set each element in the original basic.data['Air_Temp'].data to another value. (Because the main instrument was forgotten to turn on for that day, and I am using a secondary measurement data for Air Temperature for my another calculation. However it fails. Although single assignment works:
I[13]: basic.data['Air_Temp'].data[0] = 30
Shouldn't this be working like the regular NumPy arrays do?
Based on the traceback, I'd say it's because you're trying to replace the object pointed to by the .data attribute. Instead, try to just change the bits contained in .data:
basic.data['Air_Temp'].data[:] = np.ones(len(basic.data['Air_Temp']))*30
Also, you since you are setting all elements to a single value, you don't need to generate an array on the righthand side. And, you don't need to manipulate ".data" directlyI think it is best to avoid doing so. Consider:
Yep. The "data" attribute is in fact a readonly property that retuns a view of the masked array as a standard ndarray. If you need to set individual values, just do so on the masked array. If you need to mask a value, use the syntax
yourarray[yourindex] = np.ma.masked
participants (4)

Eric Firing

Gökhan Sever

Pierre GM

Ryan May