Spike functions#

AUTHORS:

William Stein (2007-07): initial version
Karl-Dieter Crisman (2009-09): adding documentation and doctests

class sage.functions.spike_function.SpikeFunction(v, eps=1e-07)#

Bases: object

Base class for spike functions.

INPUT:

v – list of pairs (x, height)
eps – parameter that determines approximation to a true spike

OUTPUT:

a function with spikes at each point x in v with the given height.

EXAMPLES:

sage: spike_function([(-3,4), (-1,1), (2,3)], 0.001)
A spike function with spikes at [-3.0, -1.0, 2.0]

Putting the spikes too close together may delete some:

sage: spike_function([(1,1), (1.01,4)], 0.1)
Some overlapping spikes have been deleted.
You might want to use a smaller value for eps.
A spike function with spikes at [1.0]

Note this should normally be used indirectly via spike_function, but one can use it directly:

sage: from sage.functions.spike_function import SpikeFunction
sage: S = SpikeFunction([(0,1), (1,2), (pi,-5)]); S                             # needs sage.symbolic
A spike function with spikes at [0.0, 1.0, 3.141592653589793]
sage: S.support                                                                 # needs sage.symbolic
[0.0, 1.0, 3.141592653589793]

plot(xmin=None, xmax=None, **kwds)#

Special fast plot method for spike functions.

EXAMPLES:

sage: S = spike_function([(-1,1), (1,40)])
sage: P = plot(S)                                                           # needs sage.plot
sage: P[0]                                                                  # needs sage.plot
Line defined by 8 points

plot_fft_abs(samples=4096, xmin=None, xmax=None, **kwds)#

Plot of (absolute values of) Fast Fourier Transform of the spike function with given number of samples.

EXAMPLES:

sage: S = spike_function([(-3,4), (-1,1), (2,3)]); S
A spike function with spikes at [-3.0, -1.0, 2.0]
sage: P = S.plot_fft_abs(8)                                                 # needs sage.plot
sage: p = P[0]; p.ydata  # abs tol 1e-8                                     # needs sage.plot
[5.0, 5.0, 3.367958691924177, 3.367958691924177, 4.123105625617661,
 4.123105625617661, 4.759921664218055, 4.759921664218055]

plot_fft_arg(samples=4096, xmin=None, xmax=None, **kwds)#

Plot of (absolute values of) Fast Fourier Transform of the spike function with given number of samples.

EXAMPLES:

sage: S = spike_function([(-3,4), (-1,1), (2,3)]); S
A spike function with spikes at [-3.0, -1.0, 2.0]
sage: P = S.plot_fft_arg(8)                                                 # needs sage.plot
sage: p = P[0]; p.ydata  # abs tol 1e-8                                     # needs sage.plot
[0.0, 0.0, -0.211524990023434, -0.211524990023434,
 0.244978663126864, 0.244978663126864, -0.149106180027477,
 -0.149106180027477]

vector(samples=65536, xmin=None, xmax=None)#

Create a sampling vector of the spike function in question.

EXAMPLES:

sage: S = spike_function([(-3,4), (-1,1), (2,3)],0.001); S
A spike function with spikes at [-3.0, -1.0, 2.0]
sage: S.vector(16)                                                          # needs sage.modules
(4.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
 0.0, 0.0, 0.0)

sage.functions.spike_function.spike_function#: alias of SpikeFunction