log

Builtin index · Core maths

result = ln(x)

Input: x · Output: result

What it is

Natural logarithm, elementwise (log is an alias for ln — it is not base-10; see log10 for that). x is a scalar, Vec, or Mat/Signal; a non-positive element gives NaN/-inf rather than an error.

Overloads

One call shape — this function is not overloaded.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

x = 0.5
print("tan={tan(x)}  asin={asin(x)}  acos={acos(x)}  atan={atan(x)}")
print("sinh={sinh(x)}  cosh={cosh(x)}  tanh={tanh(x)}")
print("ln(e^2)={ln(exp(2))}  log(e^2)={log(exp(2))}  log2(8)={log2(8)}")

z = 3 + 4j
print("arg={arg(z)}  phase={phase(z)}  re={re(z)}  imag={imag(z)}  im={im(z)}  conj={conj(z)}")

print(ceil(2.1))   # 3

tan=0.546302  asin=0.523599  acos=1.047198  atan=0.463648
sinh=0.521095  cosh=1.127626  tanh=0.462117
ln(e^2)=2  log(e^2)=2  log2(8)=3
arg=0.927295  phase=0.927295  re=3  imag=4  im=4  conj=3 - 4j
3

from core-math

How it works

log(x) is natural; log(x, base) is to that base. The second form existed in every language people arrive from and was silently discarded here -- log(8, 2) answered 2.08.

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.

See also

ln — documented in the same entry.