El dt 31 de 10 del 2006 a les 23:38 +0000, en/na George Sakkis va escriure:

Is there a more elegant and/or faster way to read some records from a file and then sort them by different fields ? What I have now is too specific and error-prone in general:

import numpy as N records = N.fromfile(a_file, dtype=N.dtype('i2,i4')) records_by_f0 = records.take(records.getfield('i2').argsort()) records_by_f1 = records.take(records.getfield('i4',2).argsort())

If there's a better way, I'd like to see it; bonus points for in-place sorting.

Why this is too specific or error-prone? I think your solution is quite good. If what you want is a more compact way to write the above, you can try with: In [56]:records=numpy.array([(1,1),(0,2)], dtype="i2,i4") In [57]:records[records['f0'].argsort()] Out[57]: array([(0, 2), (1, 1)], dtype=[('f0', 'http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642

El dc 01 de 11 del 2006 a les 15:18 +0000, en/na George Sakkis va escriure:

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Why this is too specific or error-prone?

Because it 1. repeats the field types 2. requires adding up the length of all previous fields as offset.

If you're not convinced yet, try writing this in less than 3 seconds ;-): records = N.fromfile(a_file, dtype=N.dtype('i2,i4,f4,S5,B,Q')) records_by_f5 = ??

Ah, I see your point :)

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I think your solution is quite good.If what you want is a more compact way to write the above, you can try with:

In [56]:records=numpy.array([(1,1),(0,2)], dtype="i2,i4") In [57]:records[records['f0'].argsort()] Out[57]: array([(0, 2), (1, 1)], dtype=[('f0', '

Ah, much better; I didn't know you can index a normal array (not recarray) by label. Now, if there's a way to do the sorting in place (records.sort('f1') doesn't work unfortunately), that would be perfect.

Yes, I agree that having the possibility to do records.sort('f1') would be a great addition (both in terms of usability but also efficiency). Cheers, -- Francesc Altet | Be careful about using the following code -- Carabos Coop. V. | I've only proven that it works, www.carabos.com | I haven't tested it. -- Donald Knuth ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642

Albert Strasheim wrote:

Check the thread "Strange results when sorting array with fields" from about a week back. Travis made some changes to sorting in the presence of fields that should solve your problem, assuming your fields appear in the order you want to sort (i.e. you want to sort f1, f2, f3 and not something like f1, f3, f2).

I'm afraid this won't help in my case; I want to sort twice, once by f1 and once by f2. I guess I could make a second file with the fields swapped but this seems more messy and inefficient than Francesc's suggestion. George ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642

Charles R Harris wrote:

On 11/1/06, George Sakkis wrote:

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Albert Strasheim wrote:

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Check the thread "Strange results when sorting array with fields" from about a week back. Travis made some changes to sorting in the presence of fields that should solve your problem, assuming your fields appear in the order you want to sort (i.e. you want to sort f1, f2, f3 and not something like f1, f3, f2).

I'm afraid this won't help in my case; I want to sort twice, once by f1 and once by f2. I guess I could make a second file with the fields swapped but this seems more messy and inefficient than Francesc's suggestion.

Do you actually want the two different orders, or do you want to sort on the first field, then sort all the items with the same first field on the second field?

The former. George ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642

George Sakkis wrote:

Albert Strasheim wrote:

...

Check the thread "Strange results when sorting array with fields" from about a week back. Travis made some changes to sorting in the presence of fields that should solve your problem, assuming your fields appear in the order you want to sort (i.e. you want to sort f1, f2, f3 and not something like f1, f3, f2).

I'm afraid this won't help in my case; I want to sort twice, once by f1 and once by f2. I guess I could make a second file with the fields swapped but this seems more messy and inefficient than Francesc's suggestion.

As a final contribution before I become more quiet for a few weeks (and aside from hopefully releasing 1.0.1 soon), I've added a feature to allow specifying the sorting order for record arrays. It's added to the sort method as the order= keyword. You can pass in a string (specifying which field comes first --- all other fields will stay in the same order) or you can pass in a list or tuple which indicates the field order (any fields un-specified will stay in their same relative order). It works be creating a new data-type object with the .names attribute replaced with a newly ordered one and then calling sort on a view of the array with that data-type. The VOID_compare uses the names tuple to determine the ordering. This was the un-named option in my previous list. It's a better solution than all of the others, I think. The newly created data-type is discarded after the sorting is complete. -Travis ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642