DATA MINING Desktop Survival Guide by Graham Williams
Desktop Survival Project Home List of Figures List of Tables Data Mining Data Mining Data Mining with Rattle Introduction Data Transform Explore A Model Building Framework Unsupervised Modelling Two Class Models Multi Class Models Regression Models Text Mining Evaluation and Deployment Moving into R Troubleshooting R for the Data Miner R Data Graphics in R Understanding Data Preparing Data Building Models Evaluating Models Algorithms Apriori Bagging Bayes Classifier Boosting Cluster Analysis Conditional Trees Hierarchical Clustering K-Means K-Nearest Neighbours Linear Models Logistic Regression Neural Networks Support Vector Machines Text Mining Open Products AlphaMiner Borgelt Data Mining Suite KNime R Rattle Weka Closed Products C4.5 Clementine Equbits Foresight GhostMiner InductionEngine ODM Enterprise Miner Statistica Data Miner TreeNet Virtual Predict Appendicies Glossary Bibliography Index

Logical

Objects of type logical take on the values TRUE or FALSE. The basic logical operators include:

!	Not	$<$	Less than	$<=$	Less than or equal to
$==$	Equal to	$>$	Greater than	$>=$	Greater than or equal to
&	And	|	Or	&& ||	Non vectorised versions

> 5 == 4        # FALSE
> 5 != 4 	# TRUE
> ! 1 - 1	# TRUE since 1-1 is 0 and is coerced to FALSE
> TRUE * 2	# 2 since TRUE is coerced to 1.

The single logical connectives & and | operates on vectors, whilst the double connective returns a single result, and does a minimal amount of comparison to get the result.

> c(TRUE, TRUE, FALSE) & c(TRUE, FALSE, FALSE)
[1]  TRUE FALSE FALSE
> c(TRUE, TRUE, FALSE) && c(TRUE, FALSE, FALSE)
[1] TRUE

The double form is usually what you want in an if statement.

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