% fields, Tools for spatial data
% Copyright 2004-2011, Institute for Mathematics Applied Geosciences
% University Corporation for Atmospheric Research
% Licensed under the GPL -- www.gpl.org/licenses/gpl.html

\name{fields testing scripts}
\alias{fields.tests}
\alias{test.for.zero}

\title{
Testing fields functions
}
\description{

Some of the basic methods in fields can be tested by directly
implementing the linear algebra using matrix expressions and
other functions can be cross checked within fields. These
comparisons are done in the the R source code test files in the tests
subdirectory of fields.  The function \code{test.for.zero} is useful for
comparing the tests in a meaninful and documented way. 
}

\usage{
test.for.zero( xtest,xtrue,  tol= 1.0e-8, relative=TRUE, tag=NULL)
}

\arguments{

\item{xtest}{Vector of target values}

\item{xtrue}{Vector of reference values}

\item{tol}{Tolerance to judge whether the test passes.}

\item{relative}{If true a relative error comparison is used. (See
 details below.)}

\item{tag}{ A text string to be printed out with the test results as a
   reference}

}

\details{
The scripts in the \code{tests} subdirectory are 

\describe{
\item{Krig.test.R:}{Tests basic parts of the Krig and Tps functions including replicated
and weighted observations. }

\item{Krig.se.test.R:}{Tests computations of standard errors for the
Kriging estimate.}

\item{Krig.se.grid.test.R}{Tests approximate standard errors for the
Krig function found by Monte Carlo conditional simulation.} 

\item{Krig.test.W.R}{Tests predictions and A matrix  when an off diagonal 
observation weight matrix is used.}

\item{Krig.se.W.R}{Tests standard errors when an off diagonal 
observation weight matrix is used.}

\item{spam.test.R}{Tests sparse matrix formats and linear algebra.}

\item{Wend.test.R}{Tests form for Wendland covariance family and its
use of sparse matrix formats.}

\item{diag.multiply.test.R}{Tests special (efficient) version of matrix 
multiply for diagonal matrices.}

\item{ evlpoly.test.R}{Tests evaluation of univariate and multivariate
polynomial evaluation.}

\item{mKrig.test.R}{Tests the micro Krig function with and without sparse 
matrix methods. }


}

To run the tests just attach the fields library and source the testing
file.  In the the fields source code these are in a subdirectory
"tests". Compare the output to the "XXX.Rout.save" text file. 
Keeping in mind that no test messages should print if all is well, this is
really a formality. The main reason these comparisions are provided is for 
matching the conventions of the R package checking utilities. 

 \code{test.for.zero} is used to print out the result for each
individual comparison.
Failed tests are potentially very bad and are reported with a
string beginning 

"FAILED test value = ... "

If the object test.for.zero.flag exists (it can have any value),
all the tests that pass print  text beginning,

 "    PASSED  test at tolerance ..."

This startegy means that if all tests succeed nothing and the
\code{object test.for.zero.flag} does not exist then nothing is printed
in the test scripts.  This is option simplifies the output scripts for
running through the tests -- no news is good news. 


FORM OF COMPARISON:
The actual test done is the sum of absolute differnces:

test value = \code{ 
sum( abs(c(xtest) - c( xtrue) ) ) /denom}

Where \code{demon} is either  \code{ mean( abs(c(xtrue)))} for relative error
or 1.0 otherwise. 

Note the use of "c" here to stack any structure in xtest and xtrue into
a vector. 

}
 
\keyword{misc}