how to delete from a list?

[Felix]

hi,

�

I have an entry level question:

�

say you have a� list

temp:�`a`b`c`d`e`f`g`h

i have an index list

bad:2 3 4

�

does anyone know how to remove the indexs in bad from temp?

�

thanks!

--
CHEN, Cheng

[wp]

this is one way, assuming bad is sorted:q)temp _/ bad+neg til count badOn Sun, Jul 17, 2011 at 12:39 PM, CHEN, Cheng wrote:> hi,>> I have an entry level question:>> say you have a� list> temp:�`a`b`c`d`e`f`g`h> i have an index list> bad:2 3 4>> does anyone know how to remove the indexs in bad from temp?>> thanks!>> --> CHEN, Cheng>> --> You received this message because you are subscribed to the Google Groups> "Kdb+ Personal Developers" group.> To post to this group, send email to personal-kdbplus@googlegroups.com.> To unsubscribe from this group, send email to> personal-kdbplus+unsubscribe@googlegroups.com.> For more options, visit this group at> http://groups.google.com/group/personal-kdbplus?hl=en.>

[wp]

in place:

q).[`temp;();_/;bad+neg til count bad]

[_Oz_]

temp{x _ y}/bad

or

temp @ (til count temp) except bad

[Daniel]

temp except temp[bad]On Jul 17, 7:39�pm, "CHEN, Cheng" wrote:> hi,>> I have an entry level question:>> say you have a �list> temp: `a`b`c`d`e`f`g`h> i have an index list> bad:2 3 4>> does anyone know how to remove the indexs in bad from temp?>> thanks!>> --> CHEN, Cheng

[wp]

unfortunately temp except temp[bad] doesn't guarantee you won't delete
elements you don't want to delete.

temp{x _ y}/bad is not really what was asked as indexes will shift
while using over.

[_Oz_]

sorry about 1) , you are absolutely right 🙂

2) should work for you though

[David_J_Roberts]

a reliable and simple answer is: �temp[(til count temp) except bad]

but: �temp except temp bad ��is quicker if you have unique symbols

/ is overkill (bad joke)

q)temp:100000?`$/:.Q.a

q)bad:10000?til 100

q)\t do[100; temp _/ bad+neg til count bad]

252

q)\t do[100;�temp[(til count temp) except bad]]

55

q)\t do[100; temp except temp bad]

36

David.

[David_J_Roberts]

Though, as walter says, in the special condition where bad is sorted, using over is slightly quicker:

q)bad:asc 10000?til 100

q)\t do[100; temp _/ bad+neg til count bad]

31

[simon1]

q)temp:100000?`$/:.Q.a

q)bad:10000?til 100

q)\t do[100; temp _/ bad+neg til count bad]

1465

q)\t do[100; temp[(til count temp) except bad]]

113

q)\t do[100;{t:(count x)#1b;t[y]:0b;x where t}[temp;bad]]

44

[Aaron_Davies]

To: personal-kdbplus@googlegroups.comX-Mailer: Apple Mail (2.1084)> say you have a list> temp: `a`b`c`d`e`f`g`h> i have an index list> bad:2 3 4> > does anyone know how to remove the indexs in bad from temp?temp:temp til[count temp]except bad