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Mirrors

Around two or three months ago I changed the position of the side mirrors on our car.

This is from an article in Car and Driver which was linked by lifehacker.  Check it out - it has completely changed my driving experience.  I drive in rush hour and in NYC traffic every day, and being able to see my (former) "blind spot" without twisting is an absolute joy.  If I look in the rearview mirror I see what's behind me, and when I look in the side mirrors I see what's next to me.  Once a passing car leaves the side mirror's view it's in full, normal, forward-facing view.

I suggest that if you try this, at the beginning continue to check your blind spot as you normally would until you get used to the new view.  You'll naturally gradually stop that check as you get comfortable.

One caveat, though, parking is more difficult, since you can't actually see the side of your car anymore.  You'll need to lean to get that view in the mirror.  But, in my opinion, it's well worth it for far safer driving the rest of the time.

And You Thought I Wasn't Going to Post

It may be a bit late, but here it is. As I said last week I would post a picture from my Graduation.

Of course i was joined by my parents, Eli and my Grandmother.

For more from my graduation check out my mother blog.

Triumphant Return

Well I am back. I should be blogging weekly once again. In fact next week post will be a follow up of this weeks post. Yesterday I graduated with a Bachelor of Science in Mechanical and Aerospace Engineering with Honors and as a J.J. Slade Scholar (which I will explain another week). Unfortunately because it was just yesterday I have not yet gotten the pictures from those people who had cameras. However, I can give you teasers, see if you can pick me out and of course my back as I receive an empty folder. Chag Shavuot Sameach.

Finals

Last week I proctored a physics lab final exam at YU.  YU does not allow students to have cellphones on them while they take exams:

Our exam didn't allow a calculator and apparently someone was so desperate they were praying, until someone made them leave their siddur up front.

The northern lights

I went to Labrador - didn't see the northern lights but I heard a lot about them. The locals all had interesting opinions about when they come out. Here are a few of the highlights:

• "You can only see them in the summertime, I see them all the time then."
• "It needs to be a very chilly night"
• "Its usually above a river, something in the moisture makes them appear"
• "They only come out in the winter, and never in the summer"
• "You need to walk outside at night and whistle then they will come out"

Note that when people said these things they were stating them as facts, not theories. They truly believed it.

(photo from emagine-travel.co.uk)

A stupid map

I noticed this sign up in Marshak Hall at City College:

Although it's a pretty good Photoshop, it's pretty silly.  Even if we disregard the overly green trees, evenly carpeting the NJ side of the Hudson River (even the sheer cliffs of the Palisades).

You see, lower Manhattan is mostly landfill:

See interactive map here: http://www.pbs.org/wgbh/amex/newyork/maps/maps_pop.html
If man didn't affect the island, it would look drastically different than just covered with trees.

Matlab Programs

Last week I finally published two matlab programs that you might find useful. In this post I will describe the programs, why I made them and how you can use them.

In my opinion, Matlab's built in Error-bar function could be a lot better. By default it plots a spindly blue wisp of an error bar connected to its little friends. People that I know mostly use errorbars for bar plots, where this kind of graphic looks ridiculous. It is possible to modify parameters and setting in order to get matlabs errorbars to look the way you want, but as a result of an hour of confusion and a function call that runs off the page.

Also, it is extremely difficult to plot errorbars onto a group bar plot. My function, errorb or "create healthy looking error bars" takes the same input as Matlab's function and plots nice error bars as a default. It can also plot in color, just the tops, with varying linewidths and different widths of the little hats on top. It can also plot the bars horizontally.

Here is a screenshot from a function call:

The function is free and you can download it here: error bars.

The next function I tackled is the histogram function. In case you don't know what a histogram is I'm going to start with the screenshot:

If you call Matlab's histogram function, by default it breaks the range of your data into 10 bins and bar-plots it. In case you want more bins you can specify the number, but if you have a few outliers (points far from the main distribution) then its hard to capture it on one plot. Even then you can still change settings to make things reasonable but if you have to do it "by hand" for each plot you make. Things become even more confusing if you need to compare different graphs. This function will make all these tasks much easier as well as doing some fancy things you might not have asked for like output text that you might want to use for a figure caption.

Summary of what function does:

1. Automatically sets the number and range of the bins to be appropriate for the data.
2. Compares multiple sets of data elegantly on one or more plots, with legend or titles. It also graphs the mean and standard deviations. It can also plot the median and mode of each plot.
3. Outputs text with the useful statistics for each distribution.
4. Allows for changing many more parameters

There are really a lot of features that this function has, and you can see them all in the help file in the header of the function. It will also show you how to use it. On this page I'm just going to say what the function can do in an attempt to convince you to use it.

The key advantage of this function is that it allows you to plot multiple sets of data all at once, and for easy comparison. The default behaviour plots the discrete probability density of each one together by normalizing the area under the histogram to one. Also, to make things comparable when there are different bin sizes, the bin sizes are automatically set to be multiples of each other. In case you don't like different bin sizes, you can also choose to have them plotted with identical bins. In case you don't like them all on one plot then you can also have them plotted above each other on separate plots, but with the same axis bounds so they are stil comparable. In this case the legend will be replaced with subplot titles. But then your figure may become squished once you plot a few graphs. If you think this may be a problem you can set it to automatically expand the figure size if you are plotting a lot of data.

Note that the mean and standard deveation of the

distribution are by default plotted above the graph, but you can also turn it off. Also, the median and or the mode can be added to the graph with a stem plot.

The 'optimal' bin size that is chosen is actually a theoretical measure from "Scott's choice" where 'h' is the bin width, sigma is the standard deviation and 'n' is the number of data points in the set. The axis bounds are chosen by my own simple algorithm of setting it to be 4 times the standard deviation away from the mean (or the minimum of the data set). You can change this number from 4 to any you like, or set hard axis bounds.

The function returns a string with the plotname, mean, standard deviation, and the number of points that may fall outside the range plotted. You can also ask it to return a lot more text, including median, mode, number of total points and standard error.

The function can also return the number of items in each bin,

and the locations of the left edges of each bin.

The function is free and you can download it here: Plot and compare nice histograms by default

Lastly I have to thank Eli, Avi and the AP-Lab for all their help in designing these functions.

And on a side note: I now have an official "Authors" page on the Mathworks website, where I am ranked 978 with 120 downloads in just under a week. Lets hope this goes up!