Preface to First Edition - lib

COMPUTING WITH DATA 19R> layout(matrix(1:2, nrow = 2))R> hist(Forbes2000$marketvalue)R> hist(log(Forbes2000$marketvalue))Histogram of Forbes2000$marketvalueFrequency0 10000 50 100 150 200 250 300 350Forbes2000$marketvalueHistogram of log(Forbes2000$marketvalue)Frequency0 400 800−4 −2 0 2 4 6log(Forbes2000$marketvalue)Figure 1.1Histograms of the market value and the logarithm of the market valuefor the companies contained in the Forbes 2000 list.market value may be visually compared in Figure 1.4. Prior to calling theplot function on our data, we have to remove empty levels from the countryvariable, because otherwise the x-axis would show all and not only the selectedcountries. This task is most easily performed by subsetting the correspondingfactor with additional argument drop = TRUE. Here, the width of the boxesare proportional to the square root of the number of companies for each countryand extremely large or small market values are depicted by single points.More elaborate graphical methods will be discussed in Chapter 2.© 2010 by Taylor and Francis Group, LLC