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Lips that taste of tears, they say, are the best for kissing.Dorothy Parkerget crankymore quotes

genomes: fun



EMBO Practical Course: Bioinformatics and Genome Analysis, 5–17 June 2017.


visualization + design

Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca

Working with senior graphics editor at Scientific American Jen Christiansen, I have designed three Graphic Science visualizations for the magazine.

Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
December 2015. Composition of bacteria in household dust.
Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
June 2015. Relationship between genes and traits.
Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
September 2014. Similarity of human, Denisovan, chimp, bonobo, and gorilla genomes.

Men and Women Alter a Home's Bacteria Differently

An analysis of dust reveals how the presence of men, women, dogs and cats affects the variety of bacteria in a household

December 2015, Scientific American Volume 313, Issue 6

This collaboration with Jeanine Hunnicutt explored differences in household dust bacteria based on the gender and pet status of the occupants.

We have also written about the making of the graphic, for those interested in how these things come together.

Graphic by Martin Krzywinski and Barbara Jeanine Hunnicutt.

Catalogue of bacteria shapes by Barbara Jeanine Hunnicutt.

Source: Barberan A et al. (2015) The ecology of microscopic life in household dust. Proc. R. Soc. B 282: 20151139.

Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca

A Road Map to the "Volume Control" of Genes

Genes, traits and disease are linked in complex and surprising ways

June 2015, Scientific American Volume 312, Issue 6

Because sometimes only a network hairball will do.

Graphic by Martin Krzywinski.

Source: Integrative analysis of 111 reference human epigenomes. (2015) Nature 518:317.

Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca

Tiny Genetic Differences between Humans and Other Primates Pervade the Genome

Genome comparisons reveal the DNA that distinguishes Homo sapiens from its kin

September 2014, Scientific American Volume 311, Issue 3

A Scientific American blog entry "A Monkey's Blueprint" accompanies this piece. I also have a more detailed description with links to data sources.

You can also read more about Hilbert curves and creatures that live on it, Hilbertonians.

This design won a bronze award at Malofiej 23. For more information about Malofiej, see the SA Visual blog entry "There's No Infographic without Info (and other Lessons from Malofiej)".

Graphic by Martin Krzywinski, illustrations by Portia Sloan Rollings.

Scientific American Graphic Science - Martin Krzywinski. / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
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news + thoughts

Ensemble methods: Bagging and random forests

Mon 16-10-2017
Many heads are better than one.

We introduce two common ensemble methods: bagging and random forests. Both of these methods repeat a statistical analysis on a bootstrap sample to improve the accuracy of the predictor. Our column shows these methods as applied to Classification and Regression Trees.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
Nature Methods Points of Significance column: Ensemble methods: Bagging and random forests. (read)

For example, we can sample the space of values more finely when using bagging with regression trees because each sample has potentially different boundaries at which the tree splits.

Random forests generate a large number of trees by not only generating bootstrap samples but also randomly choosing which predictor variables are considered at each split in the tree.

Krzywinski, M. & Altman, N. (2017) Points of Significance: Ensemble methods: bagging and random forests. Nature Methods 14:933–934.

Background reading

Krzywinski, M. & Altman, N. (2017) Points of Significance: Classification and regression trees. Nature Methods 14:757–758.

...more about the Points of Significance column

Classification and regression trees

Mon 16-10-2017
Decision trees are a powerful but simple prediction method.

Decision trees classify data by splitting it along the predictor axes into partitions with homogeneous values of the dependent variable. Unlike logistic or linear regression, CART does not develop a prediction equation. Instead, data are predicted by a series of binary decisions based on the boundaries of the splits. Decision trees are very effective and the resulting rules are readily interpreted.

Trees can be built using different metrics that measure how well the splits divide up the data classes: Gini index, entropy or misclassification error.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
Nature Methods Points of Significance column: Classification and decision trees. (read)

When the predictor variable is quantitative and not categorical, regression trees are used. Here, the data are still split but now the predictor variable is estimated by the average within the split boundaries. Tree growth can be controlled using the complexity parameter, a measure of the relative improvement of each new split.

Individual trees can be very sensitive to minor changes in the data and even better prediction can be achieved by exploiting this variability. Using ensemble methods, we can grow multiple trees from the same data.

Krzywinski, M. & Altman, N. (2017) Points of Significance: Classification and regression trees. Nature Methods 14:757–758.

Background reading

Lever, J., Krzywinski, M. & Altman, N. (2016) Points of Significance: Logistic regression. Nature Methods 13:541-542.

Altman, N. & Krzywinski, M. (2015) Points of Significance: Multiple Linear Regression Nature Methods 12:1103-1104.

Lever, J., Krzywinski, M. & Altman, N. (2016) Points of Significance: Classifier evaluation. Nature Methods 13:603-604.

Lever, J., Krzywinski, M. & Altman, N. (2016) Points of Significance: Model Selection and Overfitting. Nature Methods 13:703-704.

Lever, J., Krzywinski, M. & Altman, N. (2016) Points of Significance: Regularization. Nature Methods 13:803-804.

...more about the Points of Significance column

Personal Oncogenomics Program 5 Year Anniversary Art

Wed 26-07-2017

The artwork was created in collaboration with my colleagues at the Genome Sciences Center to celebrate the 5 year anniversary of the Personalized Oncogenomics Program (POG).

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
5 Years of Personalized Oncogenomics Program at Canada's Michael Smith Genome Sciences Centre. The poster shows 545 cancer cases. (left) Cases ordered chronologically by case number. (right) Cases grouped by diagnosis (tissue type) and then by similarity within group.

The Personal Oncogenomics Program (POG) is a collaborative research study including many BC Cancer Agency oncologists, pathologists and other clinicians along with Canada's Michael Smith Genome Sciences Centre with support from BC Cancer Foundation.

The aim of the program is to sequence, analyze and compare the genome of each patient's cancer—the entire DNA and RNA inside tumor cells— in order to understand what is enabling it to identify less toxic and more effective treatment options.

Principal component analysis

Thu 06-07-2017
PCA helps you interpret your data, but it will not always find the important patterns.

Principal component analysis (PCA) simplifies the complexity in high-dimensional data by reducing its number of dimensions.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
Nature Methods Points of Significance column: Principal component analysis. (read)

To retain trend and patterns in the reduced representation, PCA finds linear combinations of canonical dimensions that maximize the variance of the projection of the data.

PCA is helpful in visualizing high-dimensional data and scatter plots based on 2-dimensional PCA can reveal clusters.

Altman, N. & Krzywinski, M. (2017) Points of Significance: Principal component analysis. Nature Methods 14:641–642.

Background reading

Altman, N. & Krzywinski, M. (2017) Points of Significance: Clustering. Nature Methods 14:545–546.

...more about the Points of Significance column