esterhui's blag

Be sure to check out taxview.org, a site I put together for visualizing the US federal budget.

We’ve had a lot of rain in LA recently; this also means snow in the mountains. Here are some pictures of the view of the mountains from Pasadena, makes me want to hit the slopes :/ *sigh*

I recently went to Colombia for a short (~2 week) vacation with friends from Colorado. Our motley crew included Jack, Tiff, Drew, Missy and me. The others arrived in Bogota, the capital of Colombia Friday the 13th of November 2009, one day before me. Here is a picture taken just minutes before landing at Bogota’s Eldorado airport.

Shortly after arriving in Bogota, I met up with my friends and we walked to the “Museo del Oro” (Gold Museum). Now, I’m not one who cares much for museums, but this one was pretty cool, we saw SPACE INVADERS!

Oh yes, here you can see the rest of my travel buddies. All crazy-people (currently) hailing from Boulder, Colorado, USA.

Bogota proper sports a population of just a tad bit over 7 million people. La Candelaria, where we staid, is a neighbourhood in the older part of Bogota. The neighbourhood is right next to the mountains, providing for some amazing views – the people also really enjoy their colours and grafiti

That’s it for now, more stories to come about crazy Colombia adventures.

Tags: bogota

The challenge

Back in… what? 2006,  I went to the doctor for a routine checkup, he was concerned that my blood pressure might look a tad bit high. He continued to explain sometimes the stress of going to the doctor’s office might artificially increase your blood pressure, and I should go to a pharmacy where you can get your blood pressure measured for free.

The experiment

Well, I decided why not one-up that idea and buy a cheap personal blood pressure/heart rate monitor? I recorded my heart rate and blood pressure almost every day for about a year, sometimes more than once a day. I know, they say you should make these measurements all at the same time, usually just after waking up, but I… got lazy ok? As a side note, I got very little exercise over this period, I’m curious how these plots will look now, since I exercise pretty much every day.

Heart rate over 1 year of measurements (2006), not taken at the same time every day.

The time series of my heart rate (above) seems noisy. Let’s have a look at the histogram of that:

Histogram of heart rate for 2006 (180 measurements). Looks like a Ricean distribution with mean~=64 bpm

Mean of 64 bpm? That is definitely not cool. I’ll have to start taking some data for 2010 and hope that exercising 5+ times a week brought that average down!

Let’s have a look at blood pressure. Below is a time series of both systolic and diastolic blood pressure:

Time series for SYStolic and DIAstolic blood pressure for 2006

We can look at the distribution for both these measurements as well:

Systolic blood pressure distribution appears quite gaussian with a mean of 133

Diastolic blood pressure distribution for 2006. Mean is 79

So over a 1 year average, my blood pressure was 133/79 and average heart rate 64 bpm. It’s not horrible, but something like 120/80 with a heart rate of, say, 50, would be way cooler. Perhaps that is the goal for 2010?

Instrument Calibration

Getting back to the original story line, I showed these graphs to the doctor. Needless to say, he was not impressed. I insisted that this data needs to be traceable back to a ‘national standard’, so to speak. So the doctor used his standard-issue blood pressure device, while 10 minutes later I used my electronic gadget to make (hopefully) the same measurement. It turns out the Doctor’s device was always about 10 points below mine. He decided to use this one measurement to refute all my data: obviously my device is wrong.

After he made his one measurement, he declared that my blood pressure is fine and there’s nothing to worry about. Bah.

Sitting in my favourite coffee shop, drinking my favourite drink, ready to update this blag, I realised that I left the crucial data at home that I wanted to write about today. So… it will just have to wait. Today is my ‘day off’, which means I go in to work, blast my music (because nobody is there) and get a lot of work done – it’s great.

Although… I was so excited about life last night that I couldn’t really sleep. You see, the problem was that I got back from work at 23:00 (11pm for you yankees) – arriving at my apartment in Old Town Pasadena on bike (yep, still biking to work), I was hot, sweaty, and definitely not ready for bed. To make matters worse, at 01:00 when I tried to sleep, I started getting hungry! So, a midnight snack and ice cream cured that and finally saw me off to bed around 02:00. I feel like the clerk in, well, Clerks: I’m not even supposed to be here! I knew if I slept in today, my whole sleep schedule would be deranged, so here I am, going to work, and not even supposed to be here.

Work is fun though, and since a post with only text is quite boring, here is a picture of my office. Oh yes, we had a 8+ hour power outage at JPL on Monday from 14:00 onwards, I took the time to rearrange my office and build this awesome command center:

Command Center at work: 30" apple cinema display accompanied by two 24" cinema displays.

It’s hard going home to my puny 27″ display after spending a few hours at the command center!

Just arrived in Mexico City, plane boarding for Bogata in… -10 minutes. Here is a funny Mexican customs form

PS. I already wish I spoke some Spanish, I pretend to know it by uttering one or two words I know, then when they respond in a burst of incoherene I shrug and say in English ’sorry, English?’

I’m waiting at the Los Angeles airport for my flight to Mexico City. It feels like I have been traveling for a while already *sigh*. I just noticed a curious thing: on my boarding pass (see photo) the boarding time is 3 hours before the departure time, let’s hope this is just a silly computer bug. Seriously, how can such mistakes be made on electronic tickets in this day and age?

I had a little trouble checking in as well, the check in clerk was convinced I needed a visa for Colombia, he took nearly 1/2 an hour convincing himself that I was in the clear.

I’ll see if I can blag from Mexico or Colombia. Until we meet again

Things are improving – I’ve found a better encoder (not as lossy) and also mounted my camera on my helmet (thanks for the suggestion Chris!). This video is of me biking to work, sped up 5 times and playing with my camera’s special effect features (shot in black and white, except for the color red). I had trouble keeping the damn camera level, you will see in this video I stop a few times and try to readjust the camera.

Camera mounted to helmet

You can view the video in HD here

Bike to work (sped up 5 times) from Stephan Esterhuizen on Vimeo.

I recently discovered mint.com, it is absolutely marvelous! It can do (among others) a few things that I love

• Connect to all your banks and automatically import transactions
• Get loan information via your banks
• Easily categorize your spending, allowing you to:
  • Create graphs of monthly spending by category (and others)
  • Keep track of your allowable budget, this means you would allocate, say, $200 for groceries per month, when it sees you have purchased more than that amount, it will sms/email you.
• Connect to my etrade.com account and keep track of my stocks (also tells me how well I’m doing compared to,say, the DOW – I’m doing worse! crap)

Anywho, this is totally great, because I almost started writing my own application to do these things this weekend. Thanks to my smart googling, I saved myself hours of programming!

Over the last six months I have very carefully synchronized two wall clocks together in my office. I then proceeded to make observations every couple of days and record how many seconds these clocks have drifted from UTC(NIST). Since these measurements are made with my eyeball, they are accurate to about 1 second RMS. As a result of this inaccuracy, I can’t tell you the wall clock stability over short periods of time, but this 1s RMS error becomes insignificant when computing the clock RATES over long periods of time.

 Over 6 months, they seems to have drifted 45 and 30 seconds away from truth. With only this one point, it is possible to establish the clock rates to be about 2e-6 seconds/second and 3e-6 seconds/second. That basically means both clocks gain 2 and 3 microseconds for every second. Another way to put it, is that the clocks have a frequency error of about 2 or 3 parts per million over many days – which is about what we expect for simple Quartz oscillators. Another important factor that I can’t measure with my 1s RMS error is the stability of the clocks. Sure, there is what appears to be a linear rate offset of the two clocks from UTC(NIST), but what is the jitter/stability of this 2 and 3ppm measurements? This jitter would give us a clue of the alan deviation of the clock, but alas, I can’t measure this easily with my eyeball.