Q语言 - 表算法（Table Arithmetic）

在本章中，我们将学习如何操作字典和表格。 让我们从词典开始 -

q)d:`u`v`x`y`z! 9 18 27 36 45                 /Creating a dictionary d
q)/ key of this dictionary (d) is given by
q)key d
`u`v`x`y`z
q)/and the value by
q)value d
9 18 27 36 45
q)/a specific value
q)d`x
27
q)d[`x]
27
q)/values can be manipulated by using the arithmetic operator +-*% as,
q)45 + d[`x`y]
72 81

如果需要修改字典值，那么修改公式可以是 -

q)@[`d;`z;*;9]
`d
q)d
u | 9
v | 18
x | 27
y | 36
q)/Example, table tab
q)tab:([]sym:`;time:0#0nt;price:0n;size:0N)
q)n:10;sym:`IBM`SAMSUNG`APPLE`MSFT
q)insert[`tab;(n?sym;("t"$.z.Z);n?100.0;n?100)]
0 1 2 3 4 5 6 7 8 9
q)`time xasc `tab
`tab
q)/ to get particular column from table tab
q)tab[`size]
12 10 1 90 73 90 43 90 84 63
q)tab[`size]+9
21 19 10 99 82 99 52 99 93 72
z | 405
q)/Example table tab
q)tab:([]sym:`;time:0#0nt;price:0n;size:0N)
q)n:10;sym:`IBM`SAMSUNG`APPLE`MSFT
q)insert[`tab;(n?sym;("t"$.z.Z);n?100.0;n?100)]
0 1 2 3 4 5 6 7 8 9
q)`time xasc `tab
`tab
q)/ to get particular column from table tab
q)tab[`size]
12 10 1 90 73 90 43 90 84 63
q)tab[`size]+9
21 19 10 99 82 99 52 99 93 72
q)/Example table tab
q)tab:([]sym:`;time:0#0nt;price:0n;size:0N)
q)n:10;sym:`IBM`SAMSUNG`APPLE`MSFT
q)insert[`tab;(n?sym;("t"$.z.Z);n?100.0;n?100)]
0 1 2 3 4 5 6 7 8 9
q)`time xasc `tab
`tab
q)/ to get particular column from table tab
q)tab[`size]
12 10 1 90 73 90 43 90 84 63
q)tab[`size]+9
21 19 10 99 82 99 52 99 93 72
q)/We can also use the @ amend too
q)@[tab;`price;-;2]
   sym      time           price     size
--------------------------------------------
  APPLE   11:16:39.779   6.388858     12
  MSFT    11:16:39.779   17.59907     10
  IBM     11:16:39.779   35.5638      1
 SAMSUNG  11:16:39.779   59.37452     90
  APPLE   11:16:39.779   50.94808     73
 SAMSUNG  11:16:39.779   67.16099     90
  APPLE   11:16:39.779   20.96615     43
 SAMSUNG  11:16:39.779   67.19531     90
  IBM     11:16:39.779   45.07883     84
  IBM     11:16:39.779   61.46716     63
q)/if the table is keyed
q)tab1:`sym xkey tab[0 1 2 3 4]
q)tab1
   sym    |   time          price     size
--------- | ----------------------------------
  APPLE   | 11:16:39.779   8.388858    12
  MSFT    | 11:16:39.779   19.59907    10
  IBM     | 11:16:39.779   37.5638     1
 SAMSUNG  | 11:16:39.779   61.37452    90
  APPLE   | 11:16:39.779   52.94808    73
q)/To work on specific column, try this
q){tab1[x]`size} each sym
1 90 12 10
q)(0!tab1)`size
12 10 1 90 73
q)/once we got unkeyed table, manipulation is easy
q)2+ (0!tab1)`size
14 12 3 92 75