Hi! Good Moorning!
Today is a holiday in my city. I’m taking the opportunity to continue studying q and kdb+.
I am currently reviewing lists. I made several examples using the selection functions.
Function: x sublist y
q) l:(1 3 5 7 2 4 6 8)
q) 3 sublist l
1 3 5
q) -3 sublist l
4 6 8
q) 3 4 sublist l / where x is an integer pair
7 2 4 6
Doubt:
How can I use a variable in place of fixed integers?
q) x:3
q) y:4
q) x y sublist l
Thanks again for your help!
Best regards!
The following will work: (x;y) sublist l
The reason being that when you place integers one space apart, kdb will implicitly convert this to a list, so
type 3 4 = 7h, a list of integers.
This is not the case for variables. For example:
q) x:{x+1}
q) y:4
q) x y
5
So as we can see in this case placing them side by side had the effect of applying x to y. So in order to preserve the behaviour, we write (x;y) to tell kdb this is explicitly a list, and not to apply them to one another
Best wishes,
Chad
Hey hope you’re enjoying your holiday:
f:{(x;y) sublist l}
f[3;4]
will give your desired result.
The reason why x y sublist l won’t work is kdb reads from right to left. It runs this command x (y sublist l).
Hope this helps,
Dan
Hi!
While looking for a solution to the question with the sublist function,
I wrote the code below to display part of a list from a point:
q)l:(1 3 5 7 9 2 4 6 8)
q)myF:{[qtd;i;l1] do[qtd; show l1[i]; i+:1]}
q)myF[4;3;l]
7
9
2
4
It is certainly not the ideal solution.
If anyone can show me an optimized code, I appreciate it.
Thanks again for your help!
Best regards!
Em terça-feira, 13 de outubro de 2020 às 11:28:40 UTC-3, Geraldo M Melo Jr escreveu:
Hi! Good Moorning!
Today is a holiday in my city. I’m taking the opportunity to continue studying q and kdb+.
I am currently reviewing lists.I made several examples using the selection functions.
Function: x sublist y
q) l:(1 3 5 7 2 4 6 8)
q) 3 sublist l
1 3 5
q) -3 sublist l
4 6 8
q) 3 4 sublist l / where x is an integer pair
7 2 4 6
Doubt:
How can I use a variable in place of fixed integers?
q) x:3
q) y:4
q) x y sublist l
Thanks again for your help!
Best regards!
q)L:1 3 5 7 2 4 6 8
q)x:3 4
q)x sublist L
7 2 4 6
q) / or..
q)x:3
q)y:4
q)(x;y)sublist L
7 2 4 6
Stephen Taylor | Librarian | Kx | +44 7713 400852 | stephen@kx.com
Stephen Taylor, good afternoon!
Thank you!
I didn’t understand the need for the integer pair to be a list.
Guys, I’m sorry for posting these simple questions.
Today is my second day with the language and I’m excited.
Solution presented:
q)l:(1 3 5 7 9 2 4 6 8)
q) x: 3
q) y: 4
q) (x; y) sublist l
Tanks!!!
Em terça-feira, 13 de outubro de 2020 às 12:16:29 UTC-3, ste...@kx.com escreveu:
q)L:1 3 5 7 2 4 6 8
q)x:3 4
q)x sublist L
7 2 4 6q) / or..
q)x:3
q)y:4
q)(x;y)sublist L
7 2 4 6
Stephen Taylor | Librarian | Kx | +44 7713 400852 | ste…@kx.com
Chad, thank you so much!
Thank you for the explanation.
This explanation complemented the solution presented by Stephen Taylor.
Best regards!
Em terça-feira, 13 de outubro de 2020 às 12:35:37 UTC-3, chad....@gmail.com escreveu:
The following will work: (x;y) sublist l
The reason being that when you place integers one space apart, kdb will implicitly convert this to a list, so
type 3 4 = 7h, a list of integers.
This is not the case for variables. For example:
q) x:{x+1}
q) y:4
q) x y
5
So as we can see in this case placing them side by side had the effect of applying x to y. So in order to preserve the behaviour, we write (x;y) to tell kdb this is explicitly a list, and not to apply them to one another
Best wishes,
Chad
Dan, thank you!
I will spend the day studying q language.
Do you have online courses?
Em terça-feira, 13 de outubro de 2020 às 12:35:50 UTC-3, dan.sh...@aquaq.co.uk escreveu:
Hey hope you’re enjoying your holiday:
f:{(x;y) sublist l}
f[3;4]
will give your desired result.
The reason why x y sublist l won’t work is kdb reads from right to left. It runs this command x (y sublist l).
Hope this helps,
Dan
Hello Geraldo
You can also drop the parentheses from around the long list. Q inherited that simple vector notation from APL; hard to believe it has been available for over half a century. (A colleague once complained: APL still an improvement on its successors.)
There are tutorials at code.kx.com/q/learn. There is much I want to improve there. So I am interested in any obstacles you encounter.
If you get a moment: what language/s have you used recently, and what excites you about what you are learning?
Best
Stephen
Stephen Taylor | Librarian | Kx | +44 7713 400852 | stephen@kx.com
Hello, Stephen.
> “There are tutorials at code.kx.com/q/learn.”
I am using your website as the main source of study.
> “So I am interested in any obstacles you encounter.”
Thanks!
> “If you get a moment: what language/s have you used recently, …”
The main languages: C/C ++, Python and Clojure.
Database: MySQL, MongoDB e Datomic.
I’m doing a postgraduate degree in Data Science.
We are using Python (Numpy, Pandas, …) and R.
> “… and what excites you about what you are learning?”
Hobbie: IOT (Arduino)
I found Q and KDB +, I fell in love :-)
Best
Geraldo
Em terça-feira, 13 de outubro de 2020 às 13:59:11 UTC-3, ste...@kx.com escreveu:
Hello Geraldo
You can also drop the parentheses from around the long list. Q inherited that simple vector notation from APL; hard to believe it has been available for over half a century. (A colleague once complained: APL still an improvement on its successors.)
There are tutorials at code.kx.com/q/learn. There is much I want to improve there. So I am interested in any obstacles you encounter.
If you get a moment: what language/s have you used recently, and what excites you about what you are learning?
Best
Stephen
Stephen Taylor | Librarian | Kx | +44 7713 400852 | ste…@kx.com
Hey AquaQ also offers online courses available here:
https://kdbtraining.aquaq.co.uk/
There’s plenty of further information about the training on the website
All The Best,
Dan
Dan, good morning!
Thank you!
I accessed the site and I’m doing the basic module for free.
Very good!
Best regards!
Geraldo
Em qua, 14 de out de 2020 11:36, Dan Sheppard <dan.sheppard@aquaq.co.uk> escreveu:
Hey AquaQ also offers online courses available here:
https://kdbtraining.aquaq.co.uk/
There’s plenty of further information about the training on the website
All The Best,
Dan