prob: Probability and Conditional Probability

In prob: Elementary Probability on Finite Sample Spaces

Description

Calculates probability and conditional probability of events.

Usage

Prob(x, ...)

## Default S3 method:
Prob(x, event = NULL, given = NULL, ...)

## S3 method for class 'ps'
Prob(x, event = NULL, given = NULL, ...)

Arguments

x	a probability space or a subset of one.
event	logical expression indicating elements or rows of space to keep: missing values are taken as false.
given	either a subset of a probability space or a logical expression indicating elements or rows of space to keep: missing values are taken as false.
...	further arguments to be passed to or from other methods.

Details

This function calculates the probability of events or subsets of a given sample space. Conditional probability is also implemented. In essence, the Prob() function operates by summing the probs column of its argument. It will find subsets on the fly if desired.

The event argument is used to define a subset of x, that is, the only outcomes used in the probability calculation will be those that are elements of x and satisfy event simultaneously. In other words, Prob(x,event) calculates Prob(intersect(x, subset(x, event))). Consequently, x should be the entire probability space in the case that event is non-null.

There is some flexibility in the given argument in that it can be either a data frame or it can be a logical expression that defines the subset. However, that flexibility is limited. In particular, if given is a logical expression, then event must also be specified (also a logical expression). And in this case, the argument x should be the entire sample space, not a subset thereof.

Value

A number in the interval [0,1].

Author(s)

G. Jay Kerns [e-mail].

See Also

probspace, iidspace

Examples

S <- rolldie(times = 3, makespace = TRUE )
Prob(S, X1+X2 > 9 )
Prob(S, X1+X2 > 9, given = X1+X2+X3 > 7 )

Example output

Loading required package: combinat

Attaching package: 'combinat'

The following object is masked from 'package:utils':

    combn

Loading required package: fAsianOptions
Loading required package: timeDate
Loading required package: timeSeries
Loading required package: fBasics
Loading required package: fOptions

Attaching package: 'prob'

The following objects are masked from 'package:base':

    intersect, setdiff, union

[1] 0.1666667
[1] 0.198895

prob documentation built on May 2, 2019, 12:20 p.m.