DRAFT: an interactive map plotting program for structural geologists

DRAFT is a FORTRAN IV program for interactive generation and compilation of geological maps at any scale for geometric analysis, using any combination or quantity of three input file types, and is designed to be simple to use by users with little experience.The input data may consist of three basic types: (1) orientation, (2) alphanumeric, or (3) streamed digitizer data. Output is to the terminal and four-pen graph plotter.All nonstandard FORTRAN IV features used are listed.     

Some modifications of a point-counting computer program for fabric analysis of axial orientations

A point-counting FORTRAN IV program for fabric analysis of axial orientations is given for an ICL System 4–70. Features include a correction for a marginal loss of scanning area when using the conventional Schmidt or grid method of scanning.     

Compare: A FORTRAN IV program for the quantitative comparison of polynomial trend surfaces

The method of polynomial trend surface analysis is used widely in the earth sciences. Many applications deal with surfaces fitted to a single variable in a particular area, but some are concerned with multiple variables, or a single variable measured in different areas. For these situations, quantitative assessments of the similarity between fitted surfaces can be obtained with a number of simple statistics, which are reviewed. A FORTRAN IV program to calculate polynomial trend surfaces up to third-order (cubic) for two data sets, and derive comparison measures, is described; and its operation is illustrated with a worked example.     

Computer construction of equal-angle fabric diagrams and program comparisons

Several existing computer programs producing fabric diagrams with symbols or contour lines are either not available, or inefficient and difficult to handle. The computer program presented here considers a 1-percent spherical counting area on the lower hemisphere, calculates the densities on a spherical grid, develops the contours, and projects them in an equal-angle mode on the meridial plane. This program is small, accurate, and efficient, handles all data points in a systematic manner, and may be easily applied in geosciences.     

A fortran IV program for foraminiferid stratigraphic correlation and paleoenvironmental interpretation

A program compiled in FORTRAN IV and executed on an IBM 360/65 computer was designed to calculate simple arithmetic parameters. These parameters aid in the correlation of numerous sequences in which there are large numbers of samples from each sequence. The parameters are tabulated in such a way as to easily facilitate further plots on triangular and Fisher α diagrams, which elucidate paleoenvironmental changes and stratigraphic breaks. The Foraminifera were studied at species, benthonic superfamily and planktonic levels. The latter two distributions are shown on cumulative percentage diagrams.The restraints and suggested potential of the program are discussed, and its possible extension outlined with particular reference to industrial micropaleontology.A sequence of Albian (Gault) Clay from Wissant, Boulonnais, northern France is discussed in detail as an example of the use of this program. It is correlated with a similar sequence from Copt Point. Folkestone, southeastern England. Both sequences are adjacent to one another, being separated geographically by the English Channel. The fluctuations in abundance of selected foraminiferid groups in both sequences are directly correlative.     

A computer program for printing geometrically accurate structural fabric diagrams

Previously-published computer programs for printing structural fabric diagrams are discussed, and attention drawn to their statistical inaccuracy. The geometry of the problem is examined and a computer solution is described. A FORTRAN program to implement the latter is presented and discussed; it processes both linear and planar data and outputs a fabric-density diagram on a line-printer, using alphabetical characters to represent density levels. An option is included for printing beta-intersection density diagrams for planar data.     

Tree-structured model diagnostics for linear regression

This paper studies model diagnostics for linear regression models. We propose two tree-based procedures to check the adequacy of linear functional form and the appropriateness of homoscedasticity, respectively. The proposed tree methods not only facilitate a natural assessment of the linear model, but also automatically provide clues for amending deficiencies. We explore and illustrate their uses via both Monte Carlo studies and real data examples.     

GENMIX—A generalized petrological mixing model program

GENMIX is an interactive FORTRAN program to solve generalized petrological mixing models of the type, biotite + sillimanite + quartz = garnet + K-feldspar + water, as well as simple mixing models of the type, basalt = andesite + olivine + pyroxene. The driving program is designed for ease of use and provides facilities for printing, editing, changing and adding analyses or oxides to the data bank from which analyses are selected for use in the model. Analyses also can have Fe ratios changed, be recalculated to sum to 100 percent, or be restored to previous values. The program is suited ideally for teaching purposes, as it is impossible to crash by incorrect data input, due to innumerable error traps and all data being read as characters before being converted to numbers.     

Dupan 3, a subroutine for the interpretation of duplicated data in geochemical analysis

Duplicated analytical results, properly obtained, can be used to estimate analytical standard deviation as a function of concentration of the analyte, with distinct advantage to other methods. A computer program is given which performs the necessary calculations and also enables the investigator to detect serious deviations from the theoretical model assumed.     

Centre and Range method for fitting a linear regression model to symbolic interval data

This paper introduces a new approach to fitting a linear regression model to symbolic interval data. Each example of the learning set is described by a feature vector, for which each feature value is an interval. The new method fits a linear regression model on the mid-points and ranges of the interval values assumed by the variables in the learning set. The prediction of the lower and upper bounds of the interval value of the dependent variable is accomplished from its mid-point and range, which are estimated from the fitted linear regression model applied to the mid-point and range of each interval value of the independent variables. The assessment of the proposed prediction method is based on the estimation of the average behaviour of both the root mean square error and the square of the correlation coefficient in the framework of a Monte Carlo experiment. Finally, the approaches presented in this paper are applied to a real data set and their performance is compared.     

Orthogonal mapping: A computer program for quantifying shape differences

Quantitative differences in the shape of two or more objects can be obtained by Orthogonal Mapping provided coincidental or analogous points can be identified on each object. The least-squares difference between each set of analogous points is determined by use of a projective transformation of a set of measured points which involves the rotation, translocation, and scaling of these points relative to a set of fixed points.     

A FORTRAN IV program for the analysis of tectonic strain using deformed elliptical markers

A FORTRAN IV computer program is presented which provides an objective approach to tectonic-strain marker analysis. The algorithms are based on the “Theta-Curve” method and include a test (chi-square, goodness of fit) to check the validity of an initially random marker deformation model. Graphically represented values of confidence versus calculated tectonic-strain estimates, are produced for critical interpretation of results.Orientation data are not dependent on any preconceived reference directions such as cleavage or bedding. The method does assume, in its undeforming procedure, that the median value of the deformed marker-orientations is equivalent to the direction of maximum extension in the finite-strain ellipse.Optional line-printer graphics in separate subroutine form are included for producing the widely accepted diagrams and may be interfaced easily with other strain-analysis programs. A data-conversion program is appended to enable the use of preexisting data sets intended for the STRANE program of Dunnet and Siddans.     

MULCOX2: a general computer program for the Cox regression analysis of multivariate failure time data

Multivariate failure time data is commonly encountered in biomedicine, because each study subject may experience multiple events or because there exists clustering of subjects such that failure times within the same cluster are correlated. MULCOX2 implements a general statistical methodology for analyzing such data. This approach formulates the marginal distributions of multivariate failure times by Cox proportional hazards models without specifying the nature of dependence among related failure times. The baseline hazard functions for the marginal models may be identical or different. A variety of statistical inference can be made regarding the effects of (possibly time-dependent) covariates on the failure rates. Although designed primarily for the marginal approach, MULCOX2 is general enough to implement several alternative methods. The program runs on any computer with a FORTRAN compiler. The running time is minimal. Two illustrative examples are provided.     

Effects of measurement errors in predictor selection of linear regression model

Measurement errors may affect the predictor selection of the linear regression model. These effects are studied using a measurement framework, where the variances of the measurement errors can be estimated without setting too restrictive assumptions about the measurement model. In this approach, the problem of measurement is solved in a reduced true score space, where the latent true score is multidimensional, but its dimension is smaller than the number of the measurable variables. Various measurement scales are then created to be used as predictors in the regression model. The stability of the predictor selection as well as the estimated predicted validity and the reliability of the prediction scales is examined by Monte Carlo simulations. Varying the magnitude of the measurement error variance four sets of predictors are compared: all variables, a stepwise selection, factor sums, and factor scores. The results indicate that the factor scores offer a stable method for predictor selection, whereas the other alternatives tend to give biased results leading more or less to capitalizing on chance.     

Petrological and geochemical mass-balance equations: an algorithm for least-square fitting and general error analysis

Least-square fitting of petrological and geochemical overdetermined linear systems is carried out by means of a rapidly converging algorithm which allows a general treatment of coefficient uncertainties. Both constrained and unconstrained solutions are presented. The modal analysis of lunar rock 10022 and stoichiometric coefficients for two coronitic reactions are so determined, as an example, from application of the proposed procedure to available chemical analyses.     

A computer program for reconstructing blocky rock geometry and analyzing single block stability

A computer program has been written to assist with stability analyses of systems in blocky rock. Usually the systems will be associated with extensive discontinuities, hard rock, and low-stress fields.The program begins with a three-dimensional region of interest around an excavation (or excavations). No discontinuities are included at this stage, and the excavation is assumed to be in solid rock. Its shape, however, can be complex, because the geometrical input specification for the rock permits any region that can be represented by an imaginary assemblage of convex polyhedra.The dominant discontinuities are introduced next, and the program subdivides the solid rock along their planes to reconstruct the hidden block structure around the excavation. If desired, alternative configurations can be created by eliminating particular blocks. The program then analyzes the stabilities of individual surface blocks by means of the procedure published previously by the author.A feature of the program is that its output is accompanied by perspective views of various configurations. The views are produced with the help of an auxiliary display package. It also is possible to expose internal sections in a perspective view merely by modifying the program's input; no special code had to be added.     

Snark—a four-dimensional trend-surface computer program

A fast FORTRAN IV computer program for trend-surface analysis by the method of least squares is presented and discussed in detail. Applications in mining are mentioned briefly. A sample run using a set of data which is widely available is described.     

A FORTRAN V program for a new classification technique: the g-mode central method

The G-mode central method is described. This method allows a large number of samples to be classified based on several variables. The classification method works without a priori knowledge of the taxonomic homogeneous units forming the statistical sample.