June 25, 2013

PSI Graph



Most people have probably been viewing the NEA PSI website constantly these past few days and for the more statistically inclined, they would probably be wondering why the NEA doesn’t just put up a graph comparison of the various PSI readings instead of their sea of numbers. The answer for most “anti white” camp, is obvious and stems from needing to “confuse the peasants”, but I’ll leave it to you to draw your own conclusions.

In any case, I wrote a quick PHP script (mainly out of boredom) to scrape the readings off the NEA website and employing Google Chart’s API, had the bar chart plotted for their three readings – the 3 hour PSI reading, 24 hour average PSI for PM10 and 24 hour average PSI for PM2.5. The API itself is pretty cool, allowing the user to just input values into an array and call a JS function to plot any type of graph (bar, chart, area, pie, etc).

What do all these readings mean and do we have the right values or standards for determining the air quality? I’m no expert, but this post explains things pretty well.  For  those who want more a modern (better) indication of the air quality and for per hour readings (which NEA is sorely missing and ministers are ignorant about) refer to the AQI and the We/Wear/Masks sites respectively. Its interesting that an NUS PhD student (Jeremy Chen) could come up with a more accurate formula for the PSI readings, but instead of adopting the formula, all NEA can do is argue that their formula is not necessarily worse. Go figure.

All things considered, I would of course advise all not to rely on any readings, but use your eyes and general feel of the environment before venturing out. I stepped outside for less than 3 minutes in what is considered  a “not-so-severe” PSI reading and came back inside with a splitting headache that lasted several hours – not to mention the severe dry throat and tearing eyes.

Stay safe folks!


There have been a few changes since the initial script I wrote, primarily how the different time intervals (hourly, 3 hourly, 24 hourly, etc) have merged to just hourly and the PM 2.5 index has been included into the main reading. As such, now only the average hourly PM2.5 readings from the NEA and AQICN are compared in the graph.


There are several other sites that are quite good for monitoring the PSI situation, in particular, I like this one:


Its a responsive site (reformats itself on mobile devices),  has a good, easy to understand graphic representation of the situation and some other information on the wind patterns and the Indonesian fires that contribute heavily to the haze. Check it out.

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