Raster Images in R Graphics

Figure 1: A typical statistical plot that is welldescribed by vector elements: polygons, rectangles, lines, and text. However, some displays of data are inherently raster . In other words, what is drawn is simply an array of values, where each value is visualized as a square or rectangular region of colour (see Figure 2). It is possible to draw such raster elements using vector primitives—a small rectangle can be drawn for each data value—but this approach leads to at least two problems: it can be very slow to draw lots of small rectangles when drawing to the screen; and it can lead to very large files if output is saved in a vector file format such as PDF (and viewing the resulting PDF file can be very slow). 26 00 8 04 00 6 63 00 1 28 02 8 28 03 2 31 00 7 24 00 5 19 00 5 16 00 4 15 00 4 22 01 0 24 00 1 28 01 9 30 00 1 28 02 1 15 00 5 09 00 8 11 00 5 28 03 6 62 00 1 27 00 3 26 00 3 62 00 2 65 00 5 84 00 4 03 00 2 20 00 2 12 01 2 22 01 3 37 01 3 14 01 6 27 00 4 49 00 6 24 01 1 08 01 1 62 00 3 12 02 6 31 01 1 43 00 1 24 01 7 68 00 3 12 00 6 24 01 0 24 02 2 08 00 1 12 00 7 01 00 5 37039_at 41237_at 37383_f_at 37420_i_at 1461_at 31508_at 41745_at 676_g_at 35016_at 38833_at 38095_i_at 1389_at 675_at 36795_at 38096_f_at 41215_s_at 37043_at 32378_at 37967_at 40369_f_at 36398_at 36798_g_at 39717_g_at 37320_at 34210_at 38968_at 32977_at 41723_s_at 36878_f_at 36773_f_at 41266_at 40570_at 40088_at 41193_at 36650_at 34362_at 38032_at 33774_at 35769_at 39327_at 35260_at 1134_at 35816_at 40480_s_at 2039_s_at 32116_at 39424_at 37413_at 38056_at 37225_at 873_at 40763_at 41448_at 32215_i_at 36092_at 1929_at 33405_at 39716_at 33193_at 40393_at 35663_at 33528_at 34098_f_at 1500_at 36149_at 34247_at 32475_at 205_g_at 31605_at 41348_at 37558_at 33936_at 38223_at 39635_at 37809_at 36873_at 1914_at 931_at 41191_at 39315_at 33358_at 35665_at 31615_i_at 34106_at 36897_at 177_at 38004_at 36777_at 37810_at 1947_g_at 41470_at 37251_s_at 34961_at 39135_at 41071_at 41401_at 38385_at 37724_at 176_at 35831_at 41478_at 1140_at 919_at 39210_at 37479_at 37193_at 33412_at 41779_at 40493_at 35256_at 37184_at 31472_s_at 1126_s_at 2036_s_at 38413_at 1973_s_at 37099_at 37978_at 40785_g_at 40784_at 1674_at 41743_i_at 41742_s_at 40504_at 1307_at 1928_s_at 1308_g_at 40953_at 33809_at 36275_at 33440_at 34699_at 32872_at 40167_s_at 33244_at 1992_at 35714_at 40692_at 41346_at 41397_at 37006_at 36536_at 37280_at 38631_at 34850_at 34789_at 41744_at 39556_at 2057_g_at 1463_at 1911_s_at 37539_at 38408_at 307_at 266_s_at 39781_at 40215_at 1039_s_at 36643_at 1007_s_at 37600_at 32562_at 402_s_at 1267_at 39837_s_at