In this article, Hans Gilde exposes the clever use of a heatmap hidden in the Bioconductor library. In his example, he describes a way to show different ‘observations’ on subjects, with the concept of time.
Financial indices, like the S&P 500 or the Dow Jones indices, are mathematically some kind of measure of overall market performance, and their calculations (usually in real-time) might not translate very well the different price movements of the underlying index components.
Combining the different features of the quantmod package (as described here), one can come up with a time-series based heatmap of some financial indices, like the S&P 500 for example.
Below is an adaptation of Hans Gilde’s ideas to the S&P 500 since 2007. Note that some symbols were removed while preparing the data. Note also how highly correlated the different components are.
library(XML) library(RColorBrewer) library(plyr) library(quantmod) library(Heatplus) # get the list of symbols l <- readHTMLTable('http://en.wikipedia.org/wiki/List_of_S%26P_500_companies')[[1]] l <- as.vector(l$Ticker) l <- l getMonthlyReturns <- function(sym) { y <- to.monthly(getSymbols(sym, auto.assign=FALSE, from='2007-01-01')) as.vector(ClCl(y)*100) } d <- unlist(llply(l, getMonthlyReturns, .progress="text")) # bounds at -10% and +10% for visual clarity d[d < -10] <- -10 d[d > 10] <- 10 heatmap_2(t(matrix(d, ncol=481)), col=brewer.pal(9, 'PuBu'), Rowv=NA, Colv=NA, do.dendro=c(FALSE,FALSE), scale='none', legend=2, main="S&P 500 since 2007 (monthly returns)") |
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