函数可以通过多种方式进行分类.在这里，我们根据它们采用的参数的数量和类型以及结果类型对它们进行了分类.功能可以是，
Atomic : 参数是原子的并产生原子结果
聚合 : 列表中的原子
统一(从列表中列出) : 扩展原子的概念，因为它们适用于列表.参数列表的计数等于结果列表的计数.
其他 : 如果该函数不是来自上述类别.
数学中的二进制运算在q中被称为二元函数 ;例如，"+".类似地，一元操作被称为 monadic函数;例如，"abs"或"floor".
q
q )abs -9.9/Absolute value，Negates -ve number&leaves non -ve number 9.9
q) all 4 5 0 -4 / Logical AND (numeric min), returns the minimum value 0b
q) /And, Or, and Logical Negation q) 1b & 1b / And (Max) 1b q) 1b|0b / Or (Min) 1b q) not 1b /Logical Negate (Not) 0b
q)asc 1 3 5 7 -2 0 4 / Order list ascending, sorted list / in ascending order i s returned `s#-2 0 1 3 4 5 7 q)/attr - gives the attributes of data, which describe how it's sorted. `s denotes fully sorted, `u denotes unique and `p and `g are used to refer to lists with repetition, with `p standing for parted and `g for grouped
q)avg 3 4 5 6 7 / Return average of a list of numeric values 5f q)/Create on trade table q)trade:([]time:3?(.z.Z-200);sym:3?(`ibm`msft`apple);price:3?99.0;size:3?100)
q)/ by - Groups rows in a table at given sym q)select sum price by sym from trade / find total price for each sym sym | price ------ | -------- apple | 140.2165 ibm | 16.11385
q)cols trade / Lists columns of a table `time`sym`price`size
q)count (til 9) / Count list, count the elements in a list and / return a single int value 9
q)\p 9999 / assign port number q)/csv - This command allows queries in a browser to be exported to excel by prefixing the query, such as http://localhost:9999/.csv?select from trade where sym =`ibm
q)/ cut - Allows a table or list to be cut at a certain point q)(1 3 5) cut "abcdefghijkl" / the argument is split at 1st, 3rd and 5th letter. "bc" "de" "fghijkl" q)5 cut "abcdefghijkl" / cut the right arg. Into 5 letters part / until its end. "abcde" "fghij" "kl"
q)/delete - Delete rows/columns from a table q)delete price from trade time sym size --------------------------------------- 2009.06.18T06:04:42.919 apple 36 2009.11.14T12:42:34.653 ibm 12 2009.12.27T17:02:11.518 apple 97
q)/distinct - Returns the distinct element of a list q)distinct 1 2 3 2 3 4 5 2 1 3 / generate unique set of number 1 2 3 4 5
q)/enlist - Creates one-item list. q)enlist 37 ,37 q)type 37 / -ve type value -7h q)type enlist 37 / +ve type value 7h
q)/fill - used with nulls. There are three functions for processing null values. The dyadic function named fill replaces null values in the right argument with the atomic left argument. q)100 ^ 3 4 0N 0N -5 3 4 100 100 -5 q)`Hello^`jack`herry``john` `jack`herry`Hello`john`Hello
q)/fills - fills in nulls with the previous not null value. q)fills 1 0N 2 0N 0N 2 3 0N -5 0N 1 1 2 2 2 2 3 3 -5 -5
q)/first - returns the first atom of a list q)first 1 3 34 5 3 1
q)/flip - Monadic primitive that applies to lists and associations. It interchange the top two levels of its argument. q)trade time sym price size ------------------------------------------------------ 2009.06.18T06:04:42.919 apple 72.05742 36 2009.11.14T12:42:34.653 ibm 16.11385 12 2009.12.27T17:02:11.518 apple 68.15909 97 q)flip trade time | 2009.06.18T06:04:42.919 2009.11.14T12:42:34.653 2009.12.27T17:02:11.518 sym | apple ibm apple price | 72.05742 16.11385 68.15909 size | 36 12 97
q)/iasc - 索引递增，返回相对于输入列表的升序排序列表的索引. q)iasc 5 4 0 3 4 9 2 3 1 4 0 5
q)/idesc - 索引降序，返回相对于输入列表的下降排序列表 q)idesc 0 1 3 4 3 2 1 0
q)/in - 在列表中，二元函数用于查询列表(右侧)关于其内容的列表. q)(2 4)in 1 2 3 10b
q)/insert - Insert statement, upload new data into a table. q)insert[`trade;((.z.Z);`samsung;48.35;99)],3 q)trade time sym price size ------------------------------------------------------ 2009.06.18T06:04:42.919 apple 72.05742 36 2009.11.14T12:42:34.653 ibm 16.11385 12 2009.12.27T17:02:11.518 apple 68.15909 97 2015.04.06T10:03:36.738 samsung 48.35 99
q)/key - 三个不同的函数，即生成+ ve整数，给出目录的内容或表/字典的键. q)key 9 0 1 2 3 4 5 6 7 8 q)key`:c: ` $ RECYCLE. BIN`Config.Msi`Documents and Settings`Drivers`Geojit`hiberfil.sys`I ..
q)/lower - 转换为小写和floor
q)lower("JoHn";`HERRY`SYM)
"john"
`herry`symq)/Max and Min / a|b and a&b q)9|7 9 q)9&5 5
q)/null - 如果是atom是一个null else参数列表中的0b q)null 1 3 3 0N $ b $ b 0001b
q)/peach - Parallel each, allows process across slaves
q)foo peach list1 / function foo applied across the slaves named in list1
'list1
q)foo:{x+27}
q)list1:(0 1 2 3 4)
q)foo peach list1 / function foo applied across the slaves named in list1
27 28 29 30 31q)/prev - returns the previous element i.e. pushes list forwards q)prev 0 1 3 4 5 7 0N 0 1 3 4 5
q)/random - syntax - n?list, gives random sequences of ints and floats q)9?5 0 0 4 0 3 2 2 0 1 q)3?9.9 0.2426823 1.674133 3.901671
q)/raze - Flattn a list of lists, removes a layer of indexing from a list of lists. for instance:
q)raze (( 12 3 4; 30 0);("hello";7 8); 1 3 4)
12 3 4
30 0
"hello"
7 8
1
3
4q)/read0 - Read in a text file q)read0 `:c:/q/README.txt / gives the contents of *.txt file
q)/read1 - Read in a q data file q)read1 `:c:/q/t1 0xff016200630b000500000073796d0074696d6500707269636…
q)/reverse - Reverse a list q)reverse 2 30 29 1 3 4 4 3 1 29 30 2 q)reverse "HelloWorld" "dlroWolleH"
q)/set - set value of a variable q)`x set 9 `x q)x 9 q)`:c:/q/test12 set trade `:c:/q/test12 q)get `:c:/q/test12 time sym price size --------------------------------------------------------- 2009.06.18T06:04:42.919 apple 72.05742 36 2009.11.14T12:42:34.653 ibm 16.11385 12 2009.12.27T17:02:11.518 apple 68.15909 97 2015.04.06T10:03:36.738 samsung 48.35 99 2015.04.06T10:03:47.540 samsung 48.35 99 2015.04.06T10:04:44.844 samsung 48.35 99
q)/ssr - String search and replace, syntax - ssr["string";searchstring;replaced-with] q)ssr["HelloWorld";"o";"O"] "HellOWOrld"
q)/string - converts to string, converts all types to a string format. q)string (1 2 3; `abc;"XYZ";0b) (,"1";,"2";,"3") "abc" (,"X";,"Y";,"Z") ,"0"
q)/sv - Scalar from vector, performs different tasks dependent on its arguments. It evaluates the base representation of numbers, which allows us to calculate the number of seconds in a month or convert a length from feet and inches to centimeters. q)24 60 60 sv 11 30 49 41449 / number of seconds elapsed in a day at 11:30:49
q)/system - allows a system command to be sent, q)system "dir *.py" " Volume in drive C is New Volume" " Volume Serial Number is 8CD2-05B2" "" " Directory of C:\\Users\\myaccount-raj" "" "09/14/2014 06:32 PM 22 hello1.py" " 1 File(s) 22 bytes"
q)/tables - list all tables q)tables ` `s#`tab1`tab2`trade
q)/til - Enumerate q)til 5 0 1 2 3 4
q)/trim - Eliminate string spaces q)trim " John " "John"
q)/vs - Vector from scaler , produces a vector quantity from a scaler quantity q)"|" vs "20150204|msft|20.45" "20150204" "msft" "20.45"
q)/xasc - Order table ascending, allows a table (right-hand argument) to be sorted such that (left-hand argument) is in ascending order q)`price xasc trade time sym price size ---------------------------------------------------------- 2009.11.14T12:42:34.653 ibm 16.11385 12 2015.04.06T10:03:36.738 samsung 48.35 99 2015.04.06T10:03:47.540 samsung 48.35 99 2015.04.06T10:04:44.844 samsung 48.35 99 2009.12.27T17:02:11.518 apple 68.15909 97 2009.06.18T06:04:42.919 apple 72.05742 36
q)/xcol - Renames columns of a table q)`timeNew`symNew xcol trade timeNew symNew price size ------------------------------------------------------------- 2009.06.18T06:04:42.919 apple 72.05742 36 2009.11.14T12:42:34.653 ibm 16.11385 12 2009.12.27T17:02:11.518 apple 68.15909 97 2015.04.06T10:03:36.738 samsung 48.35 99 2015.04.06T10:03:47.540 samsung 48.35 99 2015.04.06T10:04:44.844 samsung 48.35 99
q)/xcols - Reorders the columns of a table, q)`size`price xcols trade size price time sym ----------------------------------------------------------- 36 72.05742 2009.06.18T06:04:42.919 apple 12 16.11385 2009.11.14T12:42:34.653 ibm 97 68.15909 2009.12.27T17:02:11.518 apple 99 48.35 2015.04.06T10:03:36.738 samsung 99 48.35 2015.04.06T10:03:47.540 samsung 99 48.35 2015.04.06T10:04:44.844 samsung
q)/xdesc - Order table descending, allows tables to be sorted such that the left-hand argument is in descending order. q)`price xdesc trade time sym price size ----------------------------------------------------------- 2009.06.18T06:04:42.919 apple 72.05742 36 2009.12.27T17:02:11.518 apple 68.15909 97 2015.04.06T10:03:36.738 samsung 48.35 99 2015.04.06T10:03:47.540 samsung 48.35 99 2015.04.06T10:04:44.844 samsung 48.35 99 2009.11.14T12:42:34.653 ibm 16.11385 12
q)/xgroup - Creates nested table q)`x xgroup ([]x:9 18 9 18 27 9 9;y:10 20 10 20 30 40) 'length q)`x xgroup ([]x:9 18 9 18 27 9 9;y:10 20 10 20 30 40 10) x | y ---- | ----------- 9 | 10 10 40 10 18 | 20 20 27 | ,30
q)/xkey - Set key on table q)`sym xkey trade sym | time price size --------- | ----------------------------------------------- apple | 2009.06.18T06:04:42.919 72.05742 36 ibm | 2009.11.14T12:42:34.653 16.11385 12 apple | 2009.12.27T17:02:11.518 68.15909 97 samsung | 2015.04.06T10:03:36.738 48.35 99 samsung | 2015.04.06T10:03:47.540 48.35 99 samsung | 2015.04.06T10:04:44.844 48.35 99
系统命令控制 q 环境.它们具有以下形式 :
\ cmd [p] 其中p可以是可选的
下面讨论了一些流行的系统命令 :
q)/Tables in default namespace q)\a ,`trade q)\a .o / table in .o namespace. ,`TI
q)/ views/dependencies q)a:: x+y / global assingment q)b:: x+1 q)\b `s#`a`b
q)/ Pending views/dependencies q)a::x+1 / a depends on x q)\B / the dependency is pending ' / the dependency is pending q)\B `s#`a`b q)\b `s#`a`b q)b 29 q)a 29 q)\B `symbol$()
q)/change directory, \cd [name] q)\cd "C:\\Users\\myaccount-raj" q)\cd ../new-account q)\cd "C:\\Users\\new-account"
q)/ sets current namespace \d [namespace] q)\d /default namespace ' q)\d .o /change to .o q.o)\d `.o q.o)\d . / return to default q)key ` /lists namespaces other than .z `q`Q`h`j`o q)\d .john /change to non-existent namespace q.john)\d `.john q.john)\d . q)\d `.
q)/ Load file or directory, \l q)\l test2.q / loading test2.q which is stored in current path. ric | date ex openP closeP MCap ----------- | ------------------------------------------------- JPMORGAN | 2008.05.23 SENSEX 18.30185 17.16319 17876 HSBC | 2002.05.21 NIFTY 2.696749 16.58846 26559 JPMORGAN | 2006.09.07 NIFTY 14.15219 20.05624 14557 HSBC | 2010.10.11 SENSEX 7.394497 25.45859 29366 JPMORGAN | 2007.10.02 SENSEX 1.558085 25.61478 20390 ric | date ex openP closeP MCap ---------- | ------------------------------------------------ INFOSYS | 2003.10.30 DOW 21.2342 7.565652 2375 RELIANCE | 2004.08.12 DOW 12.34132 17.68381 4201 SBIN | 2008.02.14 DOW 1.830857 9.006485 15465 INFOSYS | 2009.06.11 HENSENG 19.47664 12.05208 11143 SBIN | 2010.07.05 DOW 18.55637 10.54082 15873
q)/ assign port number, \p q)\p 5001i q)\p 8888 q)\p 8888i
\\ - exit Exit form q.
