Q Language – Table Arithmetic
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In this chapter, we will learn how to operate on dictionaries and then tables. Let’s start with dictionaries −
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
If one needs to amend the dictionary values, then the amend formulation can be −
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
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