Detection and Identification Rate
This example demonstrates how to extend Bob by providing a new performance measurement for measuring the open-set identification
If you are reading this page through our GitHub portal and not through PyPI, note the development tip of the package may not be stable or become unstable in a matter of moments.
Go to https://pypi.python.org/pypi/xbob.measure.idmeasure to download the latest stable version of this package.
There are two options you can follow to get this package installed and operational on your computer: you can use automatic installers like pip (or easy_install) or manually download, unpack and use zc.buildout to create a virtual work environment just for this package. In both cases, the two dependences listed above will be automatically downloaded and installed.
Using an automatic installer
Using pip is the easiest (shell commands are marked with a $ signal):
$ pip install xbob.measure.idmeasure
You can also do the same with easy_install:
$ easy_install xbob.measure.idmeasure
This will download and install this package plus any other required dependencies. It will also verify if the version of Bob you have installed is compatible.
This scheme works well with virtual environments by virtualenv or if you have root access to your machine. Otherwise, we recommend you use the next option.
Download the latest version of this package from PyPI and unpack it in your working area. The installation of the toolkit itself uses buildout. You don’t need to understand its inner workings to use this package. Here is a recipe to get you started:
$ python bootstrap.py $ ./bin/buildout
These two commands should download and install all non-installed dependencies and get you a fully operational test and development environment.
The python shell used in the first line of the previous command set determines the python interpreter that will be used for all scripts developed inside this package. Because this package makes use of Bob, you must make sure that the bootstrap.py script is called with the same interpreter used to build Bob, or unexpected problems might occur.
If Bob is installed by the administrator of your system, it is safe to consider it uses the default python interpreter. In this case, the above 3 command lines should work as expected. If you have Bob installed somewhere else on a private directory, edit the file buildout.cfg before running ./bin/buildout. Find the section named buildout and edit or add the line prefixes to point to the directory where Bob is installed or built. For example:
[buildout] ... prefixes=/Users/crazyfox/work/bob/build
It is assumed you have followed the installation instructions for the package and got this package installed.
Two functions, DIR and DIR_plot, are in this package to compute and plot the detection and identification rates by given the predefined false acceptance rates. The descriptions of these function are presented below:
DIR(cmc_scores, far_list): ========================== Calculates the Detection and Identification Rate from the give input and a vector of specified false acceptance rates Keyword attributes: cmc_scores List of two-element tuples. Each of the tuples contains the negative and the positive scores for one test item. far_list Array of predefined false acceptance rates. Return: List of two-element tuples, namely detection and identificatio rate. Each of the tuples contains the probability that the rank r of the positive score and the corresponding false acceptance rate. r is computed as the number of negative scores that are higher than the positive score. DIR_plot(cmc_scores, far_list, logx = True, **kwargs): ====================================================== Plot the Detection and Identification Rate from the give input and a vector of specified false acceptance rates Keyword attributes: cmc_scores List of two-element tuples. Each of the tuples contains the negative and the positive scores for one test item. far_list Array of predefined false acceptance rates. logx Boolean input, if it is true, the x-axis is in log scale. kwargs A dictionary of extra plotting parameters, that is passed directly to matplotlib.pyplot.plot Note: This function does not initiate and save the figure instance, it only issues the plotting commands. Every user is responsible for setting up and saving the figure as it best fits his purpose.
Below, we provide an example of how to appy DIR_plot to plot the DIR curve, from the python universe:
>>> import idmeasure # predefine a list of false acceptance rates >>> FAR=[.01, 0.1, 1] #Read The four column file needs to be in the same format as described in the five_column function, and the "test label" (column 4) has to contain the test/probe file name. please refer the functions of bob.measure.load.cmc_four_column, bob.measure.load.cmc_five_column to load or generate the "cmc scores". >>> idmeasure.DIR_plot(cmc_scores, FAR) >>>pyplot.xlabel("Rank") >>>pyplot.ylabel("Identification Rate (%)") >>>pyplot.title("Detection and Identification Rate Identification Experiment") >>>pyplot.grid() >>>pyplot.savefig("eigenfaceDIR.png") >>>pyplot.close()
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