#   Copyright 2004 The Apache Software Foundation
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.
#
#------------------------------------------------------------------------------
# R source file to validate exponential distribution tests in
# org.apache.commons.math.distribution.ExponentialDistributionTest
#
# To run the test, install R, put this file and testFunctions
# into the same directory, launch R from this directory and then enter
# source("<name-of-this-file>")
#
# R functions used
# pexp(q, rate = 1, lower.tail = TRUE, log.p = FALSE) <- distribution
# qexp(p, rate = 1, lower.tail = TRUE, log.p = FALSE) <- quantiles
#------------------------------------------------------------------------------
tol <- 1E-7

# Function definitions

source("testFunctions")           # utility test functions

# function to verify distribution computations

verifyDistribution <- function(points, expected, mean, tol) {
 rDistValues <- rep(0, length(points))
    i <- 0
    for (point in points) {
        i <- i + 1
        rDistValues[i] <- pexp(point, 1/mean)
    }
    output <- c("Distribution test mean = ", mean)
    if (assertEquals(expected, rDistValues, tol, "Distribution Values")) {
        displayPadded(output, SUCCEEDED, WIDTH)
    } else {
        displayPadded(output, FAILED, WIDTH)
    }       
}

#--------------------------------------------------------------------------
cat("Exponential test cases\n")

mean <- 5

distributionValues <- c(0, 0, 0.001, 0.01, 0.025, 0.05, 0.1, 0.999,
                0.990, 0.975, 0.950, 0.900)
distributionPoints <- c(-2, 0, 0.005002502, 0.05025168, 0.1265890, 0.2564665, 0.5268026, 
                34.53878, 23.02585, 18.44440, 14.97866, 11.51293)

verifyDistribution(distributionPoints, distributionValues, mean, tol)

output <- "Probability test P(.25 < X < .75)"
if (assertEquals(0.0905214, pexp(.75, 1/mean) - pexp(.25, 1/mean), tol, "Probability value")) {
    displayPadded(output, SUCCEEDED, WIDTH)
} else {
    displayPadded(output, FAILED, WIDTH)
}      

displayDashes(WIDTH)