Log2Axis

class ketos.audio.utils.axis.Log2Axis(bins, bins_per_oct, min_value, label=None)[source]

Logarithmic axis with base 2.

The lower-edge value of bin no. $i$ is calculated from the formula,

$x_{i} = 2^{i / m} \cdot x_{0}$

where $m$ is the number of bins per octave and $x_0$ is the lower-edge value of the first bin.

Args:

bins: int: Total number of bins
bins_per_oct: int: Number of bins per octave
min_value: float: Left edge of first bin
label: str: Descriptive label. Optional

Attributes:

bins: int: Total number of bins
bins_per_oct: float: Number of bins per octave
x_min: float: Left edge of first bin
label: str: Descriptive label

Methods

`bin`(x[, truncate, closed_right])	Get bin number corresponding to a given value.
`low_edge`(b)	Get the lower-edge value of a given bin.
`resize`(bins)	Resize the axis.
`ticks_and_labels`([numeric_format, ...])	Create ticks and labels for drawing the axis.

bin(x, truncate=False, closed_right=False)[source]

Get bin number corresponding to a given value.

By default bins are closed on the left and open on the right, i.e., [a,b). Use the argument closed_right to reverse this.

If the value lies outside the axis range, a negative bin number or a bin number above N-1 will be returned. This behaviour can be changed using the argument ‘truncate’.

Args:

x: array-like: Value
truncate: bool: Return 0 if x is below the lower axis boundary and N-1 if x is above the upper boundary. Default is False.
closed_right: bool: If False, bin is closed on the left and open on the right. If True, bin is open on the left and closed on the right. Default is False.

Returns:

b: array-like: Bin number

Example:

>>> from ketos.audio.utils.axis import Log2Axis
>>> ax = Log2Axis(bins=4*8, bins_per_oct=8, min_value=200.)
>>> ax.bin([400.,800.])
array([ 8, 16])

low_edge(b)[source]

Get the lower-edge value of a given bin.

Args:

b: array-like: Bin number.

Returns:

x: array-like: Lower-edge bin value

Example:

>>> from ketos.audio.utils.axis import Log2Axis
>>> ax = Log2Axis(bins=4*8, bins_per_oct=8, min_value=200.)
>>> ax.low_edge([0,16])
array([200., 800.])

resize(bins)[source]

Resize the axis.

This operation changes the number of bins, but preserves the axis range.

Note: may result in an axis with a non-integer bins_per_oct attribute

Args:

bins: int: Number of bins

ticks_and_labels(numeric_format='.1f', num_labels=None, step=None, step_bins=-1, ticks=None)[source]

Create ticks and labels for drawing the axis.

The label density can be specified in three different ways: using the num_labels argument, the step argument, or the step_bins argument.

Args:

numeric_format: str: Numeric format for labels.
num_labels: int: Number of labels
step: float: Distance between consecutive labels.
step_bins: int: Number of bins between consecutive labels.
ticks: array-like: Specify tick positions manually. In this case, the method simply returns copies of the input array, in float and string formats.

Returns:

ticks: numpy.array: Tick positions
labels: list(str): Labels