abs · atan · atan2 · cos · erf · erfc · exp · int · log · log10 · sin · sqrt · tanh
Common Math Functions (HOC)¶ ↑
These math functions return a double precision value and take a double
precision argument. The exception is atan2()
which has two double precision arguments.
- Diagnostics:
Arguments that are out of range give an argument domain diagnostic.
These functions call the library routines supplied by the compiler.
-
abs
()¶ ↑ absolute value
>>> h.abs(-42.2) 42.2
See
Vector.abs()
for theVector
class.Note
In Python code, use Python’s
abs
function, which works on both numbers and numpy arrays:>>> abs(-42.2) 42.2 >>> abs(-3 + 4j) 5.0 >>> v = h.Vector([1, 6, -2, -65]) >>> abs(v.as_numpy()) array([ 1., 6., 2., 65.])
-
int
()¶ ↑ returns the integer part of its argument (truncates toward 0).
>>> h.int(3.14) 3.0 >>> h.int(-3.14) -3.0
Note
In Python code, use Python’s
int
function instead. The behavior is slightly different in that the Python function returns an int type instead of a double:>>> int(-3.14) -3 >>> int(3.14) 3
-
sqrt
()¶ ↑ square root
see
Vector.sqrt()
for theVector
class.Note
Consider using Python’s built in
math.sqrt
instead.
-
exp
()¶ ↑ - Description:
returns the exponential function to the base e
When exp is used in model descriptions, it is often the case that the cvode variable step integrator extrapolates voltages to values which return out of range values for the exp (often used in rate functions). There were so many of these false warnings that it was deemed better to turn off the warning message when Cvode is active. In any case the return value is exp(700). This message is not turned off at the interpreter level or when cvode is not active.
from neuron import h for i in range(6,12): print('%g %g' % (i, h.exp(i)))
Note
Consider using Python’s built in
math.exp
instead.
-
log
()¶ ↑ logarithm to the base e see
Vector.log()
for theVector
class.Note
Consider using Python’s built in
math.log
instead.
-
log10
()¶ ↑ logarithm to the base 10
see
Vector.log10()
for theVector
class.Note
Consider using Python’s built in
math.log10
instead.
-
cos
()¶ ↑ trigonometric function of radian argument.
see
Vector.sin()
Note
Consider using Python’s built in
math.cos
instead.
-
sin
()¶ ↑ trigonometric function of radian argument.
see
Vector.sin()
for theVector
class.Note
Consider using Python’s built in
math.sin
instead.
-
tanh
()¶ ↑ hyperbolic tangent. see
Vector.tanh()
for theVector
class.Note
Consider using Python’s built in
math.tanh
instead.
-
atan
()¶ ↑ returns the arc-tangent of y/x in the range \(-\pi/2\) to \(\pi/2\). (x > 0)
Note
Consider using Python’s built in
math.atan
instead.
-
atan2
()¶ ↑ - Syntax:
radians = atan2(y, x)
- Description:
- returns the arc-tangent of y/x in the range \(-\pi\) < radians <= \(\pi\). y and x can be any double precision value, including 0. If both are 0 the value returned is 0. Imagine a right triangle with base x and height y. The result is the angle in radians between the base and hypotenuse.
Example:
from neuron import h h.atan2(0,0) for i in range(-1,2): print(h.atan2(i*1e-6, 10)) for i in range(-1,2): print(h.atan2(i*1e-6, -10)) for i in range(-1,2): print(h.atan2(10, i*1e-6)) for i in range(-1,2): print(h.atan2(-10, i*1e-6)) h.atan2(10,10) h.atan2(10,-10) h.atan2(-10,10) h.atan2(-10,-10)
Note
Consider using Python’s built in
math.atan2
instead.
-
erf
()¶ ↑ normalized error function
\[{\rm erf}(z) = \frac{2}{\sqrt{\pi}} \int_{0}^{z} e^{-t^2} dt\]Note
In Python 2.7 and Python 3.2+, use
math.erf
instead.