When zero doesn't mean it and other geomathematical mischief

There is almost not a case in exploration geology, where the studied data doesn’t includes below detection limits and/or zero values, and since most of the geological data responds to lognormal distributions, these “zero data” represent a mathematical challenge for the interpretation. We need to start by recognizing that there are zero values in geology. For example the amount of quartz in a foyaite (nepheline syenite) is zero, since quartz cannot co-exists with nepheline. Another common essential zero is a North azimuth, however we can always change that zero for the value of 360°. These are known as “Essential zeros”, but what can we do with “Rounded zeros” that are the result of below the detection limit of the equipment? Amalgamation, e.g. adding Na2O and K2O, as total alkalis is a solution, but sometimes we need to differentiate between a sodic and a potassic alteration. Pre-classification into groups requires a good knowledge of the distribution of the data and the geochemical characteristics of the groups which is not always available. Considering the zero values equal to the limit of detection of the used equipment will generate spurious distributions, especially in ternary diagrams. Same situation will occur if we replace the zero values by a small amount using non-parametric or parametric techniques (imputation). The method that we are proposing takes into consideration the well known relationships between some elements. For example, in copper porphyry deposits, there is always a good direct correlation between the copper values and the molybdenum ones, but while copper will always be above the limit of detection, many of the molybdenum values will be “rounded zeros”. So, we will take the lower quartile of the real molybdenum values and establish a regression equation with copper, and then we will estimate the “rounded” zero values of molybdenum by their corresponding copper values. The method could be applied to any type of data, provided we establish first their correlation dependency. One of the main advantages of this method is that we do not obtain a fixed value for the “rounded zeros”, but one that depends on the value of the other variable. Key words: compositional data analysis, treatment of zeros, essential zeros, rounded zeros, correlation dependency

MA167exam00pdf

Exam questions and solutions in PDF

MA167exam00

Exam questions and solutions in LaTex. Diagrams for the questions are all together in the support.zip file, as .eps files

MA167exam01pdf

Exam questions and solutions in PDF

MA167exam01

Exam questions and solutions in LaTex. Diagrams for the questions are all together in the support.zip file, as .eps files

Vector Fields

Exercises and solutions about vector fields. Diagrams for the questions are all together in the support.zip file, as .eps files

Vector Calculus

Exercises and solutions about vector calculus

Vector functions and curves

Exercises and solutions about vector functions and curves.

Uffington White Horse vector art files

Vector graphic files for the Uffington White Horse in PDF, AI (Adobe Illustrator EPS) and SVG formats. I manually traced these from a photo using Xara Xtreme.

University Logo in Vector and Raster

This is a selection of University of Southampton Logos in both vector (svg) and raster (png) formats. These are suitable for use on the web or in small documents and posters. You can open the SVG files using inkscape (http://inkscape.org/download/?lang=en) and edit them directly. The University logo should not be modified and attention should be paid to the branding guidelines found here: http://www.edshare.soton.ac.uk/10481 You must always leave a space the width of an capital O in Southampton on all 4 edges of the logo. The negative space makes it appear more prominently on the page.

University Logo in Vector and Raster (Smoother Version)

These are a range of logos created in the same way as Mr Patrick McSweeny http://www.edshare.soton.ac.uk/11157. The logo has been extracted from PDF documents and is smoother and accurate to the original logo design. Many thanks to to McSweeny for publishing the logo, in SVG originally, I struggled to find it anywhere else. Files are in Inkscape SVG, PDF and PNG. From Mr Patrick McSweeney: This is a selection of University of Southampton Logos in both vector (svg) and raster (png) formats. These are suitable for use on the web or in small documents and posters. You can open the SVG files using inkscape (http://inkscape.org/download/?lang=en) and edit them directly. The University logo should not be modified and attention should be paid to the branding guidelines found here: http://www.edshare.soton.ac.uk/10481 You must always leave a space the width of an capital O in Southampton on all 4 edges of the logo. The negative space makes it appear more prominently on the page.

School of Physics and Astronomy Logo - Vector and Raster

Logo for the school of Physics and Astronomy in Inkscape SVG, PDF and high-resolution PNG format

Un metodo para conectar la proyección octogonal de un vector sobre un subespacio de R dotado de un producto escalar

Se trata de un estudio matemático sobre proyecciones octogonales. En el se analizan las diversas posibilidades y variables y se concluye con las posibles soluciones a aplicar al nuevo modelo vectorial.

Los medios de representación gráfica en la modelización en ciencias físicas : el caso del vector fuerza.

Resumen tomado de la publicación

Aproximación al vector histórico de la NEE sordoceguera en España.

Resumen tomado de la revista. Resumen en Inglés