Rename table columns

x xcol y    xcol[x;y]

Where y is a table, passed by value, and x is

• a symbol vector of length no greater than count cols y returns y with its first count x columns renamed
• a dictionary (since V3.6 2018.08.24) formed from two symbol vectors, of which the keys are all the names of columns of y, returns y with columns renamed according to the dictionary

q)\l trade.q
q)cols trade
`time`sym`price`size
q)`Time`Symbol xcol trade                   / rename first two columns
Time         Symbol price size
------------------------------
09:30:00.000 a      10.75 100
q)trade:`Time`Symbol`Price`Size xcol trade  / rename all and assign
q)cols trade
`Time`Symbol`Price`Size
q)cols(`a`c!`A`C)xcol([]a:();b:();c:())     / selected columns
A b C
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