Utility Functions

General utility functions.

autolab_core.gen_experiment_id(n=10)

Generate a random string with n characters.

Parameters

n (int) – The length of the string to be generated.

Returns

A string with only alphabetic characters.

Return type

str

autolab_core.histogram(values, num_bins, bounds, normalized=True, plot=False, color='b')

Generate a histogram plot.

Parameters

  • values (numpy.ndarray) – An array of values to put in the histogram.

  • num_bins (int) – The number equal-width bins in the histogram.

  • bounds (tuple of float) – Two floats - a min and a max - that define the lower and upper ranges of the histogram, respectively.

  • normalized (bool) – If True, the bins will show the percentage of elements they contain rather than raw counts.

  • plot (bool) – If True, this function uses pyplot to plot the histogram.

  • color (str) – The color identifier for the plotted bins.

Returns

The values of the histogram and the bin edges as ndarrays.

Return type

tuple of `:obj:`numpy.ndarray

autolab_core.skew(xi)

Return the skew-symmetric matrix that can be used to calculate cross-products with vector xi.

Multiplying this matrix by a vector v gives the same result as xi x v.

Parameters

xi (numpy.ndarray of float) – A 3-entry vector.

Returns

The 3x3 skew-symmetric cross product matrix for the vector.

Return type

numpy.ndarray of float

autolab_core.deskew(S)

Converts a skew-symmetric cross-product matrix to its corresponding vector. Only works for 3x3 matrices.

Parameters

S (numpy.ndarray of float) – A 3x3 skew-symmetric matrix.

Returns

A 3-entry vector that corresponds to the given cross product matrix.

Return type

numpy.ndarray of float

autolab_core.pretty_str_time(dt)

Get a pretty string for the given datetime object.

Parameters

dt (datetime) – A datetime object to format.

Returns

The datetime formatted as {year}_{month}_{day}_{hour}_{minute}.

Return type

str

autolab_core.filenames(directory, tag='', sorted=False, recursive=False)

Reads in all filenames from a directory that contain a specified substring.

Parameters

  • directory (str) – the directory to read from

  • tag (str) – optional tag to match in the filenames

  • sorted (bool) – whether or not to sort the filenames

  • recursive (bool) – whether or not to search for the files recursively

Returns

filenames to read from

Return type

list of str

autolab_core.sph2cart(r, az, elev)

Convert spherical to cartesian coordinates.

autolab_core.r

radius

Type

float

autolab_core.az

aziumth (angle about z axis)

Type

float

autolab_core.elev

elevation from xy plane

Type

float

Returns

  • float – x-coordinate

  • float – y-coordinate

  • float – z-coordinate

autolab_core.cart2sph(x, y, z)

Convert cartesian to spherical coordinates.

autolab_core.x

x-coordinate

Type

float

autolab_core.y

y-coordinate

Type

float

autolab_core.z

z-coordinate

Type

float

Returns

  • float – radius

  • float – aziumth

  • float – elevation