R Programming By Example

Understanding interactions with correlations

The correlation is a measure of the linear relation among two variables. Its value ranges from -1, representing a perfect inverse relation, to 1, representing a perfect direct relation. Just as we created a matrix of scatter plots, we will now create a matrix of correlations, and resulting graph is shown below. Large circles mean high absolute correlation. Blue circles mean positive correlation, while red circles mean negative correlation.

To create this plot we will use the corrplot() function from the corrplot package, and pass it the correlations data computed by the cor() function in R, and optionally some parameters for the text labels (tl), such as color (color) and size (cex).

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