Why can’t the table address this column?
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #d0d2da; background-color: #161821; background-color: rgba(22, 24, 33, 0.95)}span.s1 {font-variant-ligatures: no-common-ligatures}q))meta t
c | t f a
-----| -----
stock| s
name | s
q))t.stock
't.stock
[3] t.stock
^
Hi,
It could be that inside the error trap you aren’t referencing the actual table. Is “t” just the variable that represents the table inside a function?
q)tab
stock name
test ross
q)
q)
q)f1 `test
'length
[1] f1:{tab upsert x}
^
q))
q))meta tab
c | t f a
-----| -----
stock| s
name | s
q))
q))
q))tab.stock
,`test
q))
q)f2 tab
'length
[1] f2:{x upsert (“test”;“ross”)}
^
q))meta x
c | t f a
-----| -----
stock| s
name | s
q))
q))
q))x.stock
'x.stock
[3] x.stock
Using the function f1, I was able to access the columns using tab directly. However it seems that using tab as the input “x” I am unable to address the columns. As to why this is exactly I’m not 100%, but it appears that without using the table directly q is unable to locate the table to address the columns, in this way.
Hope this helps (if only a little)
Ross
As an alternative,
Within thesecond function, you could access the column using x`stock e.g.<o:p></o:p>
<o:p> </o:p>
q)tab:( stock:1#test;name:1#ross)<o:p></o:p>
q){x upsert (“test”;“ross”)}tab<o:p></o:p>
'length<o:p></o:p>
[1] {x upsert(“test”;“ross”)}<o:p></o:p>
^<o:p></o:p>
q))x.stock<o:p></o:p>
'x.stock<o:p></o:p>
[3] x.stock<o:p></o:p>
^<o:p></o:p>
q))x`stock<o:p></o:p>
,`test<o:p></o:p>
On Monday, January 15, 2018 at 10:26:07 AM UTC, Ross Edens wrote:
Hi,
It could be that inside the error trap you aren’t referencing the actual table. Is “t” just the variable that represents the table inside a function?
q)tab
stock name
test ross
q)
q)
q)f1 `test
'length
[1] f1:{tab upsert x}
^
q))
q))meta tab
c | t f a
-----| -----
stock| s
name | s
q))
q))
q))tab.stock
,`test
q))
q)f2 tab
'length
[1] f2:{x upsert (“test”;“ross”)}
^
q))meta x
c | t f a
-----| -----
stock| s
name | s
q))
q))
q))x.stock
'x.stock
[3] x.stock
Using the function f1, I was able to access the columns using tab directly. However it seems that using tab as the input “x” I am unable to address the columns. As to why this is exactly I’m not 100%, but it appears that without using the table directly q is unable to locate the table to address the columns, in this way.
Hope this helps (if only a little)
Ross
Dot notation only works on globals, it looks like your “t” is a local variable.
You could instead use
q){ x.col1}[tab]
{ x.col1}
'x.col1
q))\
q){ x`col1}[tab]
ab`c
Assuming your table is not keyed.
Terry
Ross & Terry,
if table t is assigned in a function I assume dot notation should work in that function!
foo2 results in an error and foo3, though very similar, does not result in an error
Is there a page in the documentation that discusses dot vs. tick notation?
Until I understand more it seems that the safest thing to do is use `tick notation to reference a column inside a function.
-Anuj
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #d0d2da; background-color: #161821; background-color: rgba(22, 24, 33, 0.95)}span.s1 {font-variant-ligatures: no-common-ligatures}q)foo2:{t:flip symnamesector!("SSS";";")0:sp500.csv; tf:t.sym}
q)foo2
't.sym
[1] foo2:{t:flip symnamesector!("SSS";";")0:sp500.csv; tf:t.sym}
^
q))foo3:{ t:(a:1,2;b:3,4); t.a}
q))foo3
1 2
q))foo4:{t:flip symnamesector!("SSS";";")0:sp500.csv; tf:t`sym}
q))foo4
AAALAAPAAPLABBVABCABTACNADBEADIADMADPADSADSKAEEAEPAESAETAFLAGNAIGAIVAIZAJGAKAMALBALGNALKALLALLEALXNAMATAMDAMEAMGAMGNAMPAMTAMZNANDVANSSA..
Hi ag,
I believe that as foo3 was called whilst still in break mode i.e. q)), it could access table t directly and run successfully. If you exit break mode and try, it should fail just like foo2. e.g.
q)foo3:{ t:(a:1,2;b:3,4); t.a}
q)foo3
't.a
[1] foo3:{ t:(a:1,2;b:3,4); t.a}
As for documentation the following links may be helpful, although a definitive answer as to why dot notation works in this way appears hard to come by:
http://code.kx.com/q4m3/2_Basic_Data_Types_Atoms/#257-constituents-and-dot-notation
https://stackoverflow.com/questions/24423100/dot-notation-with-dates
Hope this helps,
Ross
I think foo3 worked because you have a global t table lying around and it accessed that.
Check
q)t in key .
If it’s true then you have a global that it’s accessing, not the local. Delete the global and try again and I imagine foo3 would fail
q)delete t from .
Terry
Yes sorry,
Ignore the part about break mode for foo3. It is likely you have a global t that it is accessing as Terry said.
Ross