.. -*- coding: utf-8 -*-

===

 R

===

.. contents::

   :local:

Inspecting objects

==================

Info about object dimensions::

  length(c(1,2,3))

  dim(matrix(1:6, 2, 3))

  ncol(matrix(1:6, 2, 3))

  nrow(matrix(1:6, 2, 3))

Brief info about any object::

  typeof(str)

  str(c(1, 2))

  str(summary)

Debugging

=========

To mark function for debugging call::

  debug(fun, text = "", condition = NULL)

  debugonce(fun, text = "", condition = NULL)

To return function to normal execution::

  undebug(fun)

  isdebugged(fun)

You can under to debug mode in any piece of code by calling ``browser``.

``traceback`` prints out the function call stack after an error occurs; does

nothing if there's no error.

``trace`` allows you to insert debugging code into a function a specific places.

``recover`` allows you to modify the error behavior so that you can browse the

function call stack.

Profiling

=========

How long execution of expression takes (in low sec/milisec resolution)::

  system.time(expr, gcFirst = TRUE)

  unix.time(expr, gcFirst = TRUE)

``Rprof`` function enable global profiling. ``summaryRprof`` function decrypt

profiling data::

  Rprof()       ## start profiling

  Rprof(NULL)   ## suspend profiling

  Rprof(append = TRUE)  ## resume profiling

  Rprof(NULL)   ## end profiling

  summaryRprof() ## investigate profiling report

Generating random numbers

=========================

For each distribution there are exists corresponding generation function, named

with prefix ``r``::

  rnorm(n, mean = 0, sd = 1)

  rt(n, df, ncp)

  rbinom(n, size, prob)

  rpois(n, lambda)

  runif(n, min = 0, max = 1)

In order to generate predictable sequences use::

  set.seed(seed, kind = NULL, normal.kind = NULL)

Sampling from array::

  sample(x, size, replace = FALSE, prob = NULL)

  sample.int(n, size = n, replace = FALSE, prob = NULL)

  sample(1:10, 10)  ## permutation!!

  sample(1:10, 100, replace=TRUE)