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π Day 2026 Art Posters - Art for the 5%
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2026 π DAY | Art for the 5%. Digits of `\pi` hidden in plain view. (explore the art)

π Day 2026 Art Posters - Art for the 5%
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2026 π DAY | Art for the 5%. Digits of `\pi` hidden in plain view. (explore the art)

`\pi` Day 2020 Art — Digits, poetically.


Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2026 π DAY | Art for the 5%.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2025 π DAY | TTCAGT: A sequence of digits.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2024 π DAY | Explore the garden of digits.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2023 π DAY | Repeated sequence


Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2022 π DAY | three one four: a number of digits

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2021 π DAY | Good things grow for those who wait.' edition.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2020 π DAY | The piku.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2019 π DAY | Hundreds of digits, hundreds of languages and a special kids' edition.


Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2018 π DAY | Street maps to new destinations.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2017 π DAY | Imagine the sky in a new way.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2016 π APPROXIMATION DAY | What would happen if about right was right.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2016 π DAY | These digits really fall for each other.


Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2015 π DAY | A transcendental experience.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2014 π APPROXIMATION DAY | Spirals into roughness.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2014 π DAY | Hypnotizes you into looking.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2014 π DAY | Come into the fold.


Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2013 π DAY | Where it started.

Pi Day 2020 Art - Digits, poetically.
 / Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
CIRCULAR π 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.
3 Little `\pi`,
1 what
4 can you tell us?

Welcome to this year's celebration of `\pi` and mathematics. Among the chaos of COVID-19, this year `\pi` Day celebrations are short poetic emissions I call “piku”. They are brief pauses for the time.

Start by reading how piku are constructed and then browse submitted piku. Consider participating by submitting your own piku. All you need is a pen and a few (small) words. Very therapeutic.

But if the words here don't help, immerse yourself in my coronavirus art. It's quite catching.

If you enjoy poetry and words, see how I convert spam into poems in the style of ee cummings and if you like to see words arrange on page, look through my typographic art.

`\pi` day — poetically

What does this poem have to do with `\pi` day?

3 A Three and
1 a
4 one and a four.

Or this one?

1 Dust
4 in space vacuum
0
3 clogs alien
2 machines.
0
2 Bummer.
0

These are all nku (details and definitions). Like a haiku, an nku is a poem whose structure (line and syllable count) is constrained by the digits in some number `n`.

The first poem above is a piku (`\pi`ku, パイク), based on the first three digits of `\pi`. The second poem above is the nku for the date of this year's celebration 14032020.

Even `\pi` approximation day 22/7 has its own nku.

2 Roughly
2 the same
7 is frequently good enough.

Those that believe in the power of the Tau manifesto (`\tau = 2 \pi`) can create “tauku”.

6 Two times by anyone
2 equals
8 one time by anytwo, I hope.

I celebrate Tau day with equal, not double, enthusiasm and have made Tau day art.

contribute your own piku

If you would like to contribute to this year's piku celebration, email me a piku with "PIKU:" in subject line. Or, tweet it with the #piku hashtag.

3 piku are
1 not
4 hard to write but
1 good
5 ones are not easy.

news + thoughts

Happy 2026 π Day—
Art for the 5%

Fri 13-03-2026

Celebrate π Day (March 14th) and enjoy the art — but only if you're part of the 5%.

Go ahead, see what you can't see.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2026 π DAY | Art for the 5%. Shown in the style of Ishihara color test plates, the art is visible only to those with colour blindness. (details)

Ishihara's Tests for Colour Deficiency

Sun 08-03-2026

Authentic and accurate images of Ishihara's test plates photographed (and lovingly color-corrected) from the 38-plate Ishihara's Tests for Colour Deficiency.

I also provide the position, size, and color of each circle on each test plate.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
ISHIHARA'S TEST PLATE 6 | This plate is part of the set of transformation plates. If you see 5, you're ok. If you see 2, you're not. (details)
Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
ISHIHARA'S TEST PLATE 18 | This plate is part of the set of mysterious hidden plates. If you don't see anything, you're ok. If you see 5, you're not. (details)

Symmetric alternatives to the ordinary least squares regression

Wed 23-07-2025

What immortal hand or eye, could frame thy fearful symmetry? — William Blake, "The Tyger"

This month, we look at symmetric regression, which, unlike simple linear regression, it is reversible — remaining unaltered when the variables are swapped.

Simple linear regression can summarize the linear relationship between two variables `X` and `Y` — for example, when `Y` is considered the response (dependent) and `X` the predictor (independent) variable.

However, there are times when we are not interested (or able) to distinguish between dependent and independent variables — either because they have the same importance or the same role. This is where symmetric regression can help.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
Nature Methods Points of Significance column: Symmetric alternatives to the ordinary least squares regression. Geometry of quantities minimized in OLS and symmetric regression. OLS minimizes `\Sigma e_y^2` in `Y` ~ `X` and `\Sigma e_x^2` `X` ~ `Y`. Pythagorean regression minimizes AB (magenta). Geometric means regression (GMR) minimizes area of ABP (orange). Orthogonal regression (OR) minimizes HP (blue). (read)

Luca Greco, George Luta, Martin Krzywinski & Naomi Altman (2025) Points of significance: Symmetric alternatives to the ordinary least squares regression. Nat. Methods 22:1610–1612.

Beyond Belief Campaign BRCA Art

Wed 11-06-2025

Fuelled by philanthropy, findings into the workings of BRCA1 and BRCA2 genes have led to groundbreaking research and lifesaving innovations to care for families facing cancer.

This set of 100 one-of-a-kind prints explore the structure of these genes. Each artwork is unique — if you put them all together, you get the full sequence of the BRCA1 and BRCA2 proteins.

Propensity score weighting

Mon 17-03-2025

The needs of the many outweigh the needs of the few. —Mr. Spock (Star Trek II)

This month, we explore a related and powerful technique to address bias: propensity score weighting (PSW), which applies weights to each subject instead of matching (or discarding) them.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
Nature Methods Points of Significance column: Propensity score weighting. (read)

Kurz, C.F., Krzywinski, M. & Altman, N. (2025) Points of significance: Propensity score weighting. Nat. Methods 22:638–640.

Happy 2025 π Day—
TTCAGT: a sequence of digits

Thu 13-03-2025

Celebrate π Day (March 14th) and sequence digits like its 1999. Let's call some peaks.

Martin Krzywinski @MKrzywinski mkweb.bcgsc.ca
2025 π DAY | TTCAGT: a sequence of digits. The digits of π are encoded into DNA sequence and visualized with Sanger sequencing. (details)
Martin Krzywinski | contact | Canada's Michael Smith Genome Sciences CentrePHSA
Google whack “vicissitudinal corporealization”
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