log, xlog¶
Logarithms and natural logarithms
log¶
Natural logarithm
log x log[x]Where x is numeric and
- null, returns null
- 0, returns
-0w - a datetime, returns
x - otherwise, the natural logarithm of
x
q)log 1
0f
q)log 0.5
-0.6931472
q)log exp 42
42f
q)log -2 0n 0 0.1 1 42
0n 0n -0w -2.302585 0 3.73767log is a multithreaded primitive.
Implicit iteration¶
log is an atomic function.
It applies to dictionaries and tables
q)log(2;3 4)
0.6931472
1.098612 1.386294
q)k:`k xkey update k:`abc`def`ghi from t:flip d:`a`b!(10 -21 3;4 5 -6)
q)log d
a| 2.302585 1.098612
b| 1.386294 1.609438
q)log t
a b
-----------------
2.302585 1.386294
1.609438
1.098612
q)log k
k | a b
---| -----------------
abc| 2.302585 1.386294
def| 1.609438
ghi| 1.098612Domain and range¶
domain b g x h i j e f c s p m d z n u v t
range f . f f f f f f f . f f f z f f f fRange: fz
xlog¶
Logarithm
x xlog y xlog[x;y]Returns the base-xf logarithm of yf, where xf and yf are x and y cast to floats, i.e. "f"$(x;y).
Where yf is negative or zero, the result is null and negative infinity respectively.
q)2 xlog 8
3f
q)2 xlog 0.125
-3f
q)1.5 xlog 0 0.125 1 3 0n
-0w -5.128534 0 2.709511 0n
q)`float$"AC"
65 67f
q)65 xlog 67
1.00726
q)"A"xlog"C"
1.00726xlog is a multithreaded primitive.
Implicit iteration¶
xlog is an atomic function.
It applies to dictionaries and tables
q)(2;3 4)xlog(4;5 6)
2f
1.464974 1.292481
q)10 xlog d
a| 1 0.4771213
b| 0.60206 0.69897
q)10 xlog t
a b
-----------------
1 0.60206
0.69897
0.4771213
q)10 xlog k
k | a b
---| -----------------
abc| 1 0.60206
def| 0.69897
ghi| 0.4771213xlog and xexp¶
xlog is the inverse of xexp, i.e. y~x xexp x xlog y.
q)2 xexp 2 xlog -1 0 0.125 1 42
0n 0 0.125 1 42Domain and range¶
xlog | b g x h i j e f c s p m d z n u v t
---- | -----------------------------------
b | f . f f f f f f f . f f f . f f f f
g | . . . . . . . . . . . . . . . . . .
x | f . f f f f f f f . f f f . f f f f
h | f . f f f f f f f . f f f . f f f f
i | f . f f f f f f f . f f f . f f f f
j | f . f f f f f f f . f f f . f f f f
e | f . f f f f f f f . f f f . f f f f
f | f . f f f f f f f . f f f . f f f f
c | f . f f f f f f f . f f f . f f f f
s
p | f . f f f f f f f . f f f . f f f f
m | f . f f f f f f f . f f f . f f f f
d | f . f f f f f f f . f f f . f f f f
z | . . . . . . . . . . . . . . . . . .
n | f . f f f f f f f . f f f . f f f f
u | f . f f f f f f f . f f f . f f f f
v | f . f f f f f f f . f f f . f f f f
t | f . f f f f f f f . f f f . f f f fRange: f