`asof`¶

As-of join

t1 asof t2     asof[t1;t2]

Where

t1 is a table
t2 is a table or dictionary
the last key or column of t2 corresponds to a time column in t1

returns the values from the last rows matching the rest of the keys and time ≤ the time in t2.

q)show trade asof`sym`time!(`IBM;09:30:00.0)
price| 96.3e
size | 200
stop | 0b
corr | 0
cond | "T"
ex   | "D"

q)show trade asof([]sym:`AAPL`IBM;ex:"TD";time:09:30:00.0)
price size stop corr cond
-------------------------
78.14 100  0    0    T
96.3  200  0    0    T

The following examples use the mas table from TAQ.

q)`date xasc`mas       / sort by date
`mas

q)show a!mas asof a:([]sym:`A`B`C`GOOG;date:1995.01.01)
sym  date      | cusip     name                           wi ex uot
---------------| --------------------------------------------------
A    1995.01.01| 049870207 ATTWOODS PLC ADS REP5 ORD/5PNC 0  N  100
B    1995.01.01| 067806109 BARNES GROUP INCORPORATED      0  N  100
C    1995.01.01| 171196108 CHRYSLER CORP                  0  N  100
GOOG 1995.01.01|                                          0

q)show a!mas asof a:([]sym:`A`B`C`GOOG;date:2006.01.01)
sym  date      | cusip     name                      wi ex uot
---------------| ---------------------------------------------
A    2006.01.01| 00846U101 AGILENT TECHNOLOGIES, INC 0  N  100
B    2006.01.01| 067806109 BARNES GROUP INCORPORATED 0  N  100
C    2006.01.01| 172967101 CITIGROUP                 0  N  100
GOOG 2006.01.01| 38259P508 GOOGLE INC CLASS A        0  T  100

q)show a!mas asof a:([]sym:`A;date:1993.01.05 1996.05.23 2000.08.04)
sym date      | cusip     name                           wi ex uot
--------------| --------------------------------------------------
A   1993.01.05| 049870207 ATTWOODS PLC ADS REP5 ORD/5PNC 0  N  100
A   1996.05.23| 046298105 ASTRA AB CL-A ADS 1CL-ASEK2.50 0  N  100
A   2000.08.04| 00846U101 AGILENT TECHNOLOGIES  INC      0  N  100

asof is a multithreaded primitive.

aj, wj
Joins
Q for Mortals §9.9.8 As-of Joins

asof¶

`asof`¶