I have a set of ordered pairs of nonnegative integers (representing
pixels that are set in a binary image). To speed up access, I want to
produce an array s of boxes such that (x,y) is an ordered pair if and
only if y e. x {:: s . Keys would work perfectly for this except for
skipped x-values, so I work around it, essentially inserting a bogus
y-value for every x-value, and then removing it.
data=:>0 1;0 2;0 3;1 1;1 3;2 1;4 1
slice=:3 : 0
'X Y'=.|:/:~ y
m=.>:>./X
n=.>:>./Y
X=.(i.m),X
Y=.(m#n),Y
-.&n &.> X</.Y
)
slice data
+-----+---+-++-+
|1 2 3|1 3|1||1|
+-----+---+-++-+
I also have a test verb.
test=:3 : 0
y=./:~y
s=.slice y
y-:;(<"0 i.#s)(,"_ 0)&.> s
)
test data
1
Does anyone have any suggestions as to how to do this better?
Best wishes,
John
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
