replacing Nan's in a string array converted from a float array
I've created an array of strings using something like.... stringarray=self.karray.astype("|S8") If the array value is a Nan I get "1.#QNAN" in my string array. For cosmetic reasons I'd like to change this to something else, e.g. "invalid" or "inactive". My string array can be up to 100,000+ values. Is there a fast way to do this? Thanks Brennan
On Thu, May 7, 2009 at 19:36, Brennan Williams <brennan.williams@visualreservoir.com> wrote:
I've created an array of strings using something like....
stringarray=self.karray.astype("|S8")
If the array value is a Nan I get "1.#QNAN" in my string array.
For cosmetic reasons I'd like to change this to something else, e.g. "invalid" or "inactive".
My string array can be up to 100,000+ values.
Is there a fast way to do this?
Well, there is a print option that lets you change how nans are represented when arrays are printed. It is possible that this setting should also be used when converting to string arrays. However, it does not do so currently: In [9]: %push_print --nanstr invalid Precision: 8 Threshold: 1000 Edge items: 3 Line width: 75 Suppress: False NaN: invalid Inf: Inf In [10]: a = zeros(10) In [11]: a[5] = nan In [12]: a Out[12]: array([ 0., 0., 0., 0., 0., invalid, 0., 0., 0., 0.]) In [13]: a.astype('|S8') Out[13]: array(['0.0', '0.0', '0.0', '0.0', '0.0', 'nan', '0.0', '0.0', '0.0', '0.0'], dtype='|S8') You will need to use the typical approach: mask = (stringarray == '1.#QNAN') stringarray[mask] = 'invalid' This will be wasteful of memory, so with your large array size, you might want to consider breaking it into chunks and modifying the chunks in this way. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco
On Thu, May 7, 2009 at 5:36 PM, Brennan Williams < brennan.williams@visualreservoir.com> wrote:
I've created an array of strings using something like....
stringarray=self.karray.astype("|S8")
If the array value is a Nan I get "1.#QNAN" in my string array.
For cosmetic reasons I'd like to change this to something else, e.g. "invalid" or "inactive".
My string array can be up to 100,000+ values.
Is there a fast way to do this?
I think this is a bug. Making the printing of nans uniform was one of the goals of numpy 1.3, although a few bits were unfixable. However, this looks fixable. If you are using 1.3 please open a ticket and note the OS and numpy version. Chuck
Charles R Harris wrote:
On Thu, May 7, 2009 at 5:36 PM, Brennan Williams <brennan.williams@visualreservoir.com <mailto:brennan.williams@visualreservoir.com>> wrote:
I've created an array of strings using something like....
stringarray=self.karray.astype("|S8")
If the array value is a Nan I get "1.#QNAN" in my string array.
For cosmetic reasons I'd like to change this to something else, e.g. "invalid" or "inactive".
My string array can be up to 100,000+ values.
Is there a fast way to do this?
I think this is a bug. Making the printing of nans uniform was one of the goals of numpy 1.3, although a few bits were unfixable. However, this looks fixable. If you are using 1.3 please open a ticket and note the OS and numpy version.
ok looks like numpy 1.3.0rc1 on winxp
Chuck
------------------------------------------------------------------------
_______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
participants (3)
-
Brennan Williams -
Charles R Harris -
Robert Kern