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The R package SLEMI is designed to estimate channel capacity between
finite state input and multidimensional output from experimental data.
For efficient computations, it uses iterative algorithm based on
logistic regression. The core function
capacity_logreg_main() is the basic interface to all
functionalities provided in the package. A comprehensive documentation
is available in directory old_vignettes/SLEMI_vignette.pdf.
## Setup ### Requirements - Hardware + A 32 or 64 bit processor
(recommended: 64bit) + 1GHz processor (recommended: multicore for a
comprehensive analysis) + 2GB MB RAM (recommended: 4GB+, depends on the
size of experimental data) ### Requirements - Software The main software
requirement is the installation of the R environment (version: >=
3.6), which can be downloaded from R
project website and is distributed for all common operating systems.
We tested the package in R environment installed on Windows 7, 10; Mac
OS X 10.11 - 10.13 and Ubuntu 18.04 with no significant differences in
the performance. The use of a dedicated Integrated development
environment (IDE), e.g. posit is
recommended. Apart from base installation of R, SLEMI requires following
packages: 1. for installation + devtools
Each of the above packages can be installed by running >
install.packages("name_of_a_package") in the R console. ###
Installation SLEMI is on R CRAN now. Please install using
>install.packages("SLEMI")
In order to install directly from GitHub, use following commands in
R’s console >
# install.packages("devtools") # run if not installed
library(devtools)install_github("TJetka/SLEMI")
## Basic usage The package is based on a main wrapper function -
capacity_logreg_main() for calculation of channel capacity,
which calls specific methods implemented within this package. Similarly,
functions mi_logreg_main() can be used to estimate mutual
information, while prob_discr_pairwise() to compute
probabilities of discrimination between two different input states. ###
Preparing data For the calculation of channel capacity between X and Y
you need structure experimental data into a single
data.frame object with observations in rows, one column
with values of input (X), preferably of factor type and
columns with measured output (Y) of numeric type. ### Run
In order to estimate channel capacity, using basic logistic regression
model, call >
capacity_logreg_main(dataRaw, signal, response, output_path)
where: * dataRaw is a data.frame with experimental data as
described above * signal is a character indicating the name
of column in dataRaw with the input (X) *
response is a character vector indicating names of columns
in dataRaw with output (Y) variables *
output_path is a character with the directory, to which
results of the estimation should be saved ### Results The function
capacity_logreg_main returns a list, whose main elements
are * cc - channel capacity estimate (in bits) * p_opt - numeric vector
with the optimal input distribution * model - nnet object
describing fitted logistic regression model For convenience of further
analysis, this list is saved in output_path directory in a
file output.rds. In addition to that, a set of exploratory
graphs are created to visualise obtained estimates. ## Examples
Additional examples of using package with some background on information
theory is given in paper/TestingProcedures.pdf
and implemented in script paper/testing_procedures.R.
Codes used in publication are accessible from paper/paper_MP.R
and paper/paper_SI.R
respectively. ### Datasets In the manuscript describing methodological
aspects of our algorithm we present the analysis of information
transmission in NfkB pathway upon the stimulation of TNF-\(\alpha\). Experimental data from this
experiment in the form of single-cell time series are attached to the
package as a data.frame object and can be accessed using
data_nfkb variable. Each row of data_nfkb
represents a single observation of a cell. Column ‘signal’ indicates the
level of TNF-\(\alpha\) stimulation for
a given cell, while columns ‘response_T’, gives the normalised ratio of
nuclear and cytoplasmic transcription factor as described in
Supplementary Methods of the corresponding publication. ## Other
functionalities ### Additional parameters Apart from required arguments,
the function capacity_logreg_main has also other parameters
than can be used to tune the activity of the algorithm. These are *
model_out (default=TRUE) - logical, specify if
nnet model object should be saved into output file *
graphs (default=TRUE) - logical, controls
creating diagnostic plots in the output directory. *
plot_width (default = 6) - numeric, the basic
width of created plots * plot_height
(default = 4) - numeric, the basic height of created plots
* scale (default = TRUE) - logical, value
indicating if the columns of dataRaw are to be centered and
scaled, what is usually recommended for the purpose of stability of
numerical computations. From a purely theoretical perspective, such
transformation does not influence the value of channel capacity. *
lr_maxit (default = 1000) - (argument of
nnet package) a maximum number of iterations of
optimisation step in logistic regression algorithm. Set to higher value
if your data is more complex or of high dimension. *
MaxNWts (default = 5000) - (argument of
nnet package) a maximum number of parameters in logistic
regression model. Set to higher value if you data has many dimensions or
input has many states. ### Diagnostic procedures We implemented two
diagnostic procedures to control the performance of channel capacity
estimation and to measure uncertainty due to finite sample size and
model over-fitting. These include: 1. Bootstrap test - capacity is
re-calculated using \(x\)% of data,
sampled from original dataset without replacement. After repeating
procedure \(n\) times, its standard
deviation can be treated as an error of original estimate. 2.
Over-fitting test - original data is divided into Training and Testing
datasets. Then, logistic regression is estimated using \(x\)% of data (training dataset) and
integrals of channel capacity are calculated via Monte Carlo using
remaining \((1-x)\)% of data (testing
dataset). It is repeated \(n\) times.
In order to use those procedures, user must provide additional arguments
to function logreg_capacity_main(), i.e. * testing
(default=FALSE) - a logical value that turn on/off testing mode, *
TestingSeed (default= 1234) - the seed for the random number generator
used to sample original dataset, * testing_cores (default= 4) - a number
of cores to use (via doParallel package) in parallel
computing, * boot_num (default= 40) - a number of repetitions of the
bootstrap , * boot_prob (default= 0.8) - a fraction of initial
observations to use in the bootstrap, * traintest_num (default= 40) - a
number of repetitions of the overfitting test, * partition_trainfrac
(default= 0.6) - a fraction of initial observations to use as a training
dataset in the overfitting test ## Support Please mail t.jetka at
gmail.com in case of any bugs, problems and questions regarding package
or inquiries regarding information theory. ## Reference Please cite >
Jetka T, Nienałtowski K, Winarski T, Błoński S, Komorowski M (2019)
Information-theoretic analysis of multivariate single-cell signaling
responses. PLOS Computational Biology 15(7): e1007132.
https://doi.org/10.1371/journal.pcbi.1007132 ## License SLEMI is
released under the GNU license and is freely available. A comprehensive
documentation is available in directory old_vignettes/SLEMI_vignette.pdf.
These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
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