Heat map

Heat map generated from DNA microarray data reflecting gene expression values in several conditions

A heat map is a graphical representation of data where the individual values contained in a matrix are represented as colors. Fractal maps and tree maps both often use a similar system of color-coding to represent the values taken by a variable in a hierarchy.

History

The term "Heatmap" was originally coined and trademarked by software designer Cormac Kinney in 1991, to describe a 2D display depicting real time financial market information.[1]

Heat maps originated in 2D displays of the values in a data matrix. Larger values were represented by small dark gray or black squares (pixels) and smaller values by lighter squares. Sneath (1957) displayed the results of a cluster analysis by permuting the rows and the columns of a matrix to place similar values near each other according to the clustering. Jacques Bertin used a similar representation to display data that conformed to a Guttman scale. The idea for joining cluster trees to the rows and columns of the data matrix originated with Robert Ling in 1973. Ling used overstruck printer characters to represent different shades of gray, one character-width per pixel. Leland Wilkinson developed the first computer program in 1994 (SYSTAT) to produce cluster heat maps with high-resolution color graphics. The Eisen et al. display shown in the figure is a replication of the earlier SYSTAT design.

Types

A heat map, atop a color bathymetric map, indicating the probable location of missing Malaysia Airlines Flight 370 based on a Bayesian method analysis of possible flight paths of the aircraft.[2]

There are different kinds of heat maps:

Color schemes

There are many different color schemes that can be used to illustrate the heatmap, with perceptual advantages and disadvantages for each. Rainbow colormaps are often used, as humans can perceive more shades of color than they can of gray, and this would purportedly increase the amount of detail perceivable in the image. However, this is discouraged by many in the scientific community, for the following reasons:[3][4][5][6][7]

Choropleth Maps vs. Heat Maps

Choropleth maps are sometimes incorrectly referred to as heat maps. A choropleth map features different shading or patterns within geographic boundaries to show the proportion of a variable of interest, whereas the coloration a heat map (in a map context) does not correspond to geographic boundaries.[8]

Software implementations

A sample heat map created using a Surface Chart in Microsoft Excel.

Several heat map software implementations are listed here (the list is not complete):

Examples

References

Footnotes

  1. "United States Patent and Trademark Office, registration #75263259". 1993-09-01.
  2. MH370 - Definition of Underwater Search Areas (PDF) (Report). Australian Transport Safety Bureau. 3 December 2015.
  3. Borland, David; Taylor, Russell (2007). "Rainbow Color Map (Still) Considered Harmful". IEEE Computer Graphics and Applications 27 (2): 14. doi:10.1109/MCG.2007.323435. PMID 17388198.
  4. How NOT to Lie with Visualization - Bernice E. Rogowitz and Lloyd A. Treinish - IBM Thomas J. Watson Research Center, Yorktown Heights, NY
  5. Harrower, Mark; Brewer, Cynthia A. (2003). "ColorBrewer.org: An Online Tool for Selecting Colour Schemes for Maps". In Dodge, Martin; Kitchin, Rob; Perkins, Chris. The Cartographic Journal. pp. 27–37. doi:10.1179/000870403235002042. ISBN 978-0-470-98007-1.
  6. Green, D. A. (2011). "A colour scheme for the display of astronomical intensity images". Bulletin of the Astronomical Society of India 39: 289–95. arXiv:1108.5083. Bibcode:2011BASI...39..289G.
  7. Borkin, M.; Gajos, K.; Peters, A.; Mitsouras, D.; Melchionna, S.; Rybicki, F.; Feldman, C.; Pfister, H. (2011). "Evaluation of Artery Visualizations for Heart Disease Diagnosis". IEEE Transactions on Visualization and Computer Graphics 17 (12): 2479–88. doi:10.1109/TVCG.2011.192. PMID 22034369.
  8. http://www.gretchenpeterson.com/blog/archives/2694
  9. Caraux, G.; Pinloche, S. (2004). "Permut Matrix: A graphical environment to arrange gene expression profiles in optimal linear order". Bioinformatics 21 (7): 1280–1. doi:10.1093/bioinformatics/bti141. PMID 15546938.
  10. Sansoni, Silvia (1999-05-17). "Forbes Magazine Article on NeoVision Heatmaps".
  11. "Using R to draw a Heatmap from Microarray Data". Molecular Organisation and Assembly in Cells. 26 Nov 2009.
  12. "Draw a Heat Map". R Manual.
  13. http://gnuplot.sourceforge.net/demo_4.4/heatmaps.html[]
  14. http://www.mrao.cam.ac.uk/~dag/CUBEHELIX/[]
  15. "Tools & Scripts | Ashley Lab - Stanford Medicine". ashleylab.stanford.edu. Retrieved 2015-09-21.

Bibliography

External links

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