I am referring to the highest scored answer from this question.
The code to construct a correlation matrix given a table of columns is
u cor/:\:u:flip t where t is a table.
Reading right to left, I understand up till u:flip t. May I please ask for an explanation on what the rest of the code does?
Thanks
>Solution :
If you substitute for a something which gives more visual output, such as join with two vectors, it should be easier to see what the derived function cor/:\: is doing
q)"123","abc" // simple join
"123abc"
q)"123",/:"abc" // join left arg to each item of right arg
"123a"
"123b"
"123c"
q)"123",/:\:"abc" // join each item of left arg to each item of right
"1a" "1b" "1c"
"2a" "2b" "2c"
"3a" "3b" "3c"
Back to a simple example of cor
q)show t:([]a:3?1.0;b:3?1.0;c:3?1.0)
a b c
-------------------------------
0.7935513 0.6377554 0.3573039
0.2037285 0.03845637 0.02547383
0.7757617 0.8972357 0.688089
q)u cor/:\:u:flip t
| a b c
-| -----------------------------
a| 1 0.9474878 0.8529413
b| 0.9474878 1 0.975085
c| 0.8529413 0.975085 1
q)show data:value flip t; // extract the data for clarity
0.7935513 0.2037285 0.7757617
0.6377554 0.03845637 0.8972357
0.3573039 0.02547383 0.688089
q)cor[data 0;]each data // first row cor each row
1 0.9474878 0.8529413
q)cor[data 1;]each data // second row cor each row
0.9474878 1 0.975085
q)cor[data 2;]each data // last row cor each row
0.8529413 0.975085 1
q){cor[x]each data}each data // all at once
1 0.9474878 0.8529413
0.9474878 1 0.975085
0.8529413 0.975085 1
q)data cor/:\:data // derived function much nicer
1 0.9474878 0.8529413
0.9474878 1 0.975085
0.8529413 0.975085 1