Here we are now at the middle of the fourth large part of this talk.get nowheremore quotes

# pi day: curious

Scientific graphical abstracts — design guidelines

# visualization + design

81 digits of $\pi$ as a forest of trees: standard, bat cave and underwater editions. ( BUY ARTWORK )
The 2021 Pi Day art celebrates the digits of $\pi$ with a forest! Visit the bat cave and underwater ecosystems for the full experience.

# $\pi$ Day 2018 Art Posters - Stitched city road maps from around the world

2021 $\pi$ reminds us that good things grow for those who wait.' edition.
2019 $\pi$ has hundreds of digits, hundreds of languages and a special kids' edition.
2018 $\pi$ day stitches street maps into new destinations.
2017 $\pi$ day imagines the sky in a new way.

2016 $\pi$ approximation day wonders what would happen if about right was right.
2016 $\pi$ day sees digits really fall for each other.
2015 $\pi$ day maps transcendentally.
2014 $\pi$ approx day spirals into roughness.

2014 $\pi$ day hypnotizes you into looking.
2014 $\pi$ day
2013 $\pi$ day is where it started
Circular $\pi$ art and other distractions

On March 14th celebrate $\pi$ Day. Hug $\pi$—find a way to do it.

For those who favour $\tau=2\pi$ will have to postpone celebrations until July 26th. That's what you get for thinking that $\pi$ is wrong. I sympathize with this position and have $\tau$ day art too!

If you're not into details, you may opt to party on July 22nd, which is $\pi$ approximation day ($\pi$ ≈ 22/7). It's 20% more accurate that the official $\pi$ day!

Finally, if you believe that $\pi = 3$, you should read why $\pi$ is not equal to 3.

Most of the art is available for purchase as framed prints and, yes, even pillows. Sleep's never been more important — I take custom requests.

And if you've got to sleep a moment on the road
I will steer for you
And if you want to work the street alone
I'll disappear for you

This year's is the 30th anniversary of $\pi$ day. The theme of the art is bridging the world and making friends. So myself I again team up with my long-time friend and collaborator Jake Lever. I worled with Jake on the snowflake catalogue, where we build a world of flakes.

And so, this year we also build a world. We start with all the roads in the world and stitch them together in brand new ways. And if you walk more than 1 km in this world, you'll likely to be transported somewhere completely different.

This year's $\pi$ day song is Trance Groove: Paris. Why? Because it's worth to go to new places—real or imagined.

The input data set to the art are all the roads in the world, as obtained from Open Street Map.

Road segments between intersections are represented by polylines and ends at intersections are snapped together to coincide with a resolution of 5–10 meters.

There are 108,366,429 polylines and together they span about 39,930,000 km.

## extracting cities

We took 44 cities and sampled a square patch of 0.6 × 0.6 degrees of roads from the data set centered on the longitude and latitude coordinates below. This roughly corresponds to a square of 65 km × 65 km.

These center coordinates might be slightly different from the canonical ones associated with a city—I used Google Maps to center the coordinates on what I felt was a useful center for sampling streets. Below are these coordinates along with the number of polylines extracted.

$CITY LATITUDE LONGITUDE POLYLINES --------------- ------------ ------------- --------- amsterdam 52.38179720 4.90840330 98,965 bangkok 13.72635950 100.53609560 154,348 barcelona 41.38759720 2.17333560 86,575 beijing 39.90487690 116.39331750 49,867 berlin 52.51864170 13.40732310 64,336 buenos_aires -34.61566250 -58.50333750 267,432 cairo 30.05371250 31.23528970 108,524 copenhagen 55.67346250 12.58781160 45,025 doha 25.28233490 51.53479620 50,458 dublin 53.34316360 -6.24433520 44,109 edinburgh 55.94884870 -3.18828100 34,211 hong_kong 22.31338230 114.16994610 36,329 istanbul 41.03592820 28.98158110 190,938 jakarta -6.21858830 106.85252890 253,211 johannesburg -26.20653880 28.05113830 128,840 lisbon 38.73064000 -9.13667460 98,118 london 51.50838960 -0.08585320 169,164 los_angeles 34.04362360 -118.24505510 193,899 madrid 40.41671290 -3.70329570 112,495 marrakesh 31.63192610 -7.98895890 17,442 melbourne -37.88286720 145.11800540 140,817 mexico_city 19.39741470 -99.15827060 273,477 moscow 55.75202630 37.61531070 40,043 mumbai 19.18775070 72.97777590 65,316 nairobi -1.28718700 36.83157870 31,317 new_delhi 28.61245350 77.21369970 262,503 new_york 40.72187290 -73.92426750 199,652 nice 43.70006260 7.26974590 25,564 osaka 34.66944300 135.49965600 376,652 paris 48.85837360 2.29229260 175,028 prague 50.08022370 14.43002100 58,659 rome 41.89659480 12.49983650 81,370 san_francisco 37.77526950 -122.40966350 82,462 sao_paulo -23.57343700 -46.63341590 267,742 seoul 37.54869140 126.99479350 169,593 shanghai 31.22590500 121.47386710 50,036 st_petersburg 59.93029690 30.33955910 31,186 stockholm 59.32318770 18.07408060 48,321 sydney -33.86772020 151.20734660 76,820 tokyo 35.69220740 139.75613010 694,893 toronto 43.66328030 -79.38932030 73,173 vancouver 49.25782630 -123.19394300 34,081 vienna 48.20740250 16.37336040 53,669 warsaw 52.23101840 21.01639680 54,870$

Each city's road coordinates were then transformed using the equirectangular projection to make the distance between longitude meridians constant with latitude. This was done by $$\phi' \leftarrow \phi - \text{avg}(\phi)$$ $$\lambda' \leftarrow (\lambda - avg(\lambda)) \text{cos} (avg(\phi))$$

where $\phi$ is the latitude and $\lambda$ is the longitude. The average is taken over the patch of roads extracted for the city. For all steps below these transformed coordinates were used.

## copenhagen

Let's look at one city—Copenhagen—to get a feel for the data set.

The roads in and around Copenhagen. (zoom)

In the zoom crop below, you can see the intersections (dots) and the individual polylines that connect the intersections.

Downtown Copenhagen. (zoom)

Zooming in even more you can see the Christiansborg Slot, one of the Danish Palaces and the seat of the Danish Parliament (corresponding Google Map view).

In and around Christiansborg Slot (red dot) in downtown Copenhagen. (zoom)

## creating city strips

City strips were created by sampling patches of 0.015 × 0.015 degrees (after transformation). This corresponds roughly to 1.7 km.

For each position in the strip, patches were sampled in order of the digits of $\pi$ only if the number of polylines in the was $40d \le N < 40(d+1)-1$ where $d$ is the digit of $\pi$. Patches for $d=9$ only need to have $360 \le N$ polylines.

For example, the first patch is assigned to $d=3$ and it must have $120 \le N < 159$ polylines. The second patch is sampled so that its density is $40 \le N < 79$ because it is associated with the next digit, $d=1$.

Further selection on acceptable patches is performed so that the streets line up with the previous patch. Minor local adjustments and stitching are performed to make the join appear seamless.

Below is an example of a set of city strips for Amsterdam, Bangkok, Beijing, Berlin, Copenhagen, Edinburgh, Hong Kong, Johannesburg, Marrakesh and Melbourne.

On the road with 10 digits of $\pi$. City strips for Moscow, Mumbai, Nairobi, New Delhi, Nice, Prague, Rome, Stockholm, Vancouver and Warsaw. ( BUY ARTWORK )

Below I zoom in on a portion of the city strips above to show the result of the stitching—individual street patches are outlined in blue squares.

Close-up of stitched streets in a city strip.

It's interesting to see that some patches (e.g. 4th one on the bottom strip, which is Copenhagen) don't necessarily have roads that across the patch horizontally.

## creating world patches

World patches are a two-dimension version of city strips but they use more than one city.

Patches are sampled from cities based on the order of the digits of $\pi$, as arranged on a 6 × 6 grid. For example, the first row of patches corresponds to 314159 and the second 265358. Each digit is assigned to a city from which the corresponding patch is sampled.

As for city strips, patches are selected only if they align with previous patches. This is now trickier to do in two-dimensions because we must match a selected patch with up to two other patches already placed.

Unlike for city strips, there is no selection made for street density.

Below is a world patch using the following digit-to-city assignment: 0:Amsterdam, 1:Doha, 2:Marrakesh, 3:Mumbai, 4:Nairobi, 5:Rome, 6:San Francisco, 7:Seoul, 8:Shanghai and 9:Vancouver.

On the road with 36 digits of $\pi$. A world patch using Amsterdam, Doha, Marrakesh, Mumbai, Nairobi, Rome, San Francisco, Seoul, Shanghai and Vancouver ( BUY ARTWORK )

Below I zoom in on patches in the center of the image and show the cities from which the patches were sampled.

Close-up of stitched streets in a world patch.

# Music for the Moon: Flunk's 'Down Here / Moon Above'

Sat 29-05-2021

The Sanctuary Project is a Lunar vault of science and art. It includes two fully sequenced human genomes, sequenced and assembled by us at Canada's Michael Smith Genome Sciences Centre.

The first disc includes a song composed by Flunk for the (eventual) trip to the Moon.

But how do you send sound to space? I describe the inspiration, process and art behind the work.

The song 'Down Here / Moon Above' from Flunk's new album History of Everything Ever is our song for space. It appears on the Sanctuary genome discs, which aim to send two fully sequenced human genomes to the Moon. (more)

# Happy 2021 $\pi$ Day—A forest of digits

Sun 14-03-2021

Celebrate $\pi$ Day (March 14th) and finally see the digits through the forest.

The 26th tree in the digit forest of $\pi$. Why is there a flower on the ground?. (details)

This year is full of botanical whimsy. A Lindenmayer system forest – deterministic but always changing. Feel free to stop and pick the flowers from the ground.

The first 46 digits of $\pi$ in 8 trees. There are so many more. (details)

And things can get crazy in the forest.

A forest of the digits of '\pi$, by ecosystem. (details) Check out art from previous years: 2013$\pi$Day and 2014$\pi$Day, 2015$\pi$Day, 2016$\pi$Day, 2017$\pi$Day, 2018$\pi$Day and 2019$\pi` Day.

# Testing for rare conditions

Sun 30-05-2021

All that glitters is not gold. —W. Shakespeare

The sensitivity and specificity of a test do not necessarily correspond to its error rate. This becomes critically important when testing for a rare condition — a test with 99% sensitivity and specificity has an even chance of being wrong when the condition prevalence is 1%.

We discuss the positive predictive value (PPV) and how practices such as screen can increase it.

Nature Methods Points of Significance column: Testing for rare conditions. (read)

Altman, N. & Krzywinski, M. (2021) Points of significance: Testing for rare conditions. Nature Methods 18:224–225.

# Standardization fallacy

Tue 09-02-2021

We demand rigidly defined areas of doubt and uncertainty! —D. Adams

A popular notion about experiments is that it's good to keep variability in subjects low to limit the influence of confounding factors. This is called standardization.

Unfortunately, although standardization increases power, it can induce unrealistically low variability and lead to results that do not generalize to the population of interest. And, in fact, may be irreproducible.

Nature Methods Points of Significance column: Standardization fallacy. (read)

Not paying attention to these details and thinking (or hoping) that standardization is always good is the "standardization fallacy". In this column, we look at how standardization can be balanced with heterogenization to avoid this thorny issue.

Voelkl, B., Würbel, H., Krzywinski, M. & Altman, N. (2021) Points of significance: Standardization fallacy. Nature Methods 18:5–6.

# Graphical Abstract Design Guidelines

Fri 13-11-2020

Clear, concise, legible and compelling.

Making a scientific graphical abstract? Refer to my practical design guidelines and redesign examples to improve organization, design and clarity of your graphical abstracts.

Graphical Abstract Design Guidelines — Clear, concise, legible and compelling.

# "This data might give you a migrane"

Tue 06-10-2020

An in-depth look at my process of reacting to a bad figure — how I design a poster and tell data stories.

A poster of high BMI and obesity prevalence for 185 countries.