Gas station without pumps

2020 June 14

New plot for COVID-19

Filed under: Uncategorized — gasstationwithoutpumps @ 22:29
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It has been a while since the post I did on exponential and logistic growth models not working.  I’ve continued to scrape data from websites and plot the curves with gnuplot, but they have been very uninteresting—I was seeing almost linear growth in both US and CA curves, both for confirmed cases and for deaths.

I was getting a little bored with the manual data entry, and I did not have a good set of California data, because I had been too lazy to enter it daily.  So today I decided to waste a little time cloning the JHU github repository of data, and write a Python program to extract data from it.  This turned out to be messier than I thought, as JHU has changed the format of the files and data a couple of times,

I started by parsing the US-only files, because they seemed to be pretty clean and uniform, but they only go back 63 days (since 2020 April 12), so miss the early days of the pandemic.  I then started parsing the world-wide data files, which have a lot more rows (more than one per county for California) but fewer columns.  I needed to write routines that would merge data from multiple rows if I wanted state-wide numbers, and the format changed at least once, so that I had to recognize “San Diego County, CA” in “Province/State” as being the same state as “California” in “Province_State”.

It has also been a while since I’ve used matplotlib, so it took me some time to figure out how to do such simple things as requesting that logarithmic axes use plain numbers rather than 10^2 and 10^3.

Anyway, I think I’ve finally gotten the files parsed and been able to extract and plot some data.  I chose for my first plot just to plot the new cases/day vs total cases for each state, which I could not do with gnuplot (because it doesn’t provide an easy way to take the differences between adjacent days nor to do rolling-window averages.

I highlighted two states here: California, because that is the one I live in, and New York, because it has been hit the hardest with COVID-19.

New York has clearly peaked and has a declining new-case rate, while California is still slowly growing. I don’t think that the numbers, even with the per-capita scaling, are really comparable between California and New York, because the California fraction of tests that are positive has remained relatively small, and the new-case rate has tracked with the number of tests fairly well. I think that a lot of the growth in California has been due to increased testing and confirming a larger fraction of the cases, rather than an increase in the actual rate of new infections. (The hospitalization reports plotted by the LA Times indicate a slow decrease in California hospitalizations lately.)

2020 June 1

Marquee wisdom

Filed under: Uncategorized — gasstationwithoutpumps @ 21:38
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I liked the blog post a couple of weeks ago on the Butts In The Seats blog:

Marquee Messaging For Morale

Today, when I was going to Harts Fabrics to pick up my order of green ripstop nylon (for making a green screen for the videos for my class), I saw the marquee at the Rio Theater, which is more pointed than most:

Click to get a better-resolution image. The text says “Coming soon, Lysol Injections and The UV Suppositories”, “This is just an intermission”, and “Got Mask”.

2020 April 30

Improved 3D-printed nose clip for fabric masks

Filed under: Uncategorized — gasstationwithoutpumps @ 16:54
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I posted earlier about the nose clip I designed to keep my cloth masks from fogging up my glasses, based on the design from Prusa.  The nose clip was not as good a fit to my face as I wanted, and it seemed a little more complicated than necessary.  So I redesigned the clip to be easier to reshape, using parameters that could be more easily specified with OpenSCAD’s Customizer.  I tweaked it until it fit my face reasonably well.

The clip viewed from inside the mask—there are only two clips resting on the cheeks—nothing on bridge of the nose.  The band is now constant thickness except at the clips, which are longer than before, because they now lay more-or-less flat on my cheeks.

The outside view shows just a simple band.

I reduced the amount of “stringing” I got from the printer by changing the Z-seam settings to  “sharpest corner” and “expose seam”.  This change reduced the amount of trimming and filing needed to get a smooth surface on the clips. I’m still printing at 0.07mm resolution, though that is very slow, in order to get a smoother surface.

I have uploaded the new nose clip design to

2020 April 29

Charming ‘1-meter hats’ to practice social distancing

Filed under: Uncategorized — gasstationwithoutpumps @ 11:43
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According to an article in Goldthread (Coronavirus: Chinese students return to class with ‘1-meter hats’ to practice social distancing), a school in China has come up with a historically inspired way to teach social distancing: 1-meter hats.

One of the 1-meter hats from Yangzheng Elementary School. Picture copied from

There are several other cute pictures in the original article, which explains that hat designs are based on hats worn by government ministers during the Song Dynasty (supposedly to keep them from whispering to each other in morning meetings).

Perhaps we all need to make and wear hats like this.

2020 April 26

Idea Fab Labs masks

Filed under: Uncategorized — gasstationwithoutpumps @ 14:21
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Because Idea Fab Labs can’t do their normal business of providing tools and a place for makers to gather, they have been producing PPE for local healthcare and have started a new online business providing fabric masks. The mask sales are being done from the Chico branch of Idea Fab Labs, as the Santa Cruz branch is concentrating on manufacturing PPE for local healthcare.

There are many places selling masks online, but IFL have an added twist: design your own mask print:
The $40 setup fee is fairly normal for custom prints, but would make getting just one or two masks rather expensive ($60 for one mask, $80 for two). But if a store wanted to make 100 store-logo masks for all their employees, the cost would be only $16.40 each.

Idea Fab Labs also has artist-designed mask prints (which many places also provide) for $25 each, hand-sewn fabric masks for $30/3, and economy masks for $50/10 or $400/100.

If you want to design your own print and make several masks, you could use to make custom-printed fabric.  They are still shipping from North Carolina.  You can find a couple of patterns from Idea Fab Labs at


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