Chemometrics

Julien Wist / 2017 / Universidad del Valle

An up-to-date version of this notebook can be found here: https://github.com/jwist/chemometrics/



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options(repr.plot.width=3, repr.plot.height=3)

about variables

independent variables (experimental, predictors) are those that we manipulate during an experiment
dependent variables are the one we try to explain

we test the effect of IV on DV. We study the effect of age (IV) and lecture skills (IV) on academic performances (marks, DV). The latter depend on the former. A high or low mark will never affect the lecture skills.

It is important to know how many IV and DV we have, since it will guide us to pick the correct method.

https://statistics.laerd.com/statistical-guides/types-of-variable.php
http://www.allanalytics.com/author.asp?section_id=1413&doc_id=252823

categorical and continuous variables

Nominal (names: Colombia, Burkina Faso)
Dichotomous (male or female, the one usually exclude the other)
Ordinal (low, middle, high)
Continous variables
- interval (0 C is not ratio)
- ratio (0 K is a ratio, because it means no temperature at all)

decision tree

- by knowing the kind and number of variables we can use such a decision tree to guide us among the many methods It goes behond the scope of this classe to study all of them, but we will use the tree for the several example we want to study deeper in.

Ennos, R. 2007. Statistical and Data Handling Skills in Biology. Harlow, U.K., Pearson Education Limited