Creative Commons Images

I mentioned in class the other day that you should might the copyright on images that you use in your infographic. You have some leeway here, since there’s a “fair use” clause to the copyright laws in the US that covers some uses of copyrighted material in educational settings. However, going with Creative Commons images is always safe. These are images that anyone can use, as long as they attribute the creator and follow a few other stipulations that vary from image to image–like not using an image for commercial use or not altering the image in any way. See the CC license descriptions for details.

To find images with Creative Commons licenses, I recommend using Compfight to search for such images on the photo-sharing site Flickr. Just search for a term or terms (like “elephants“), then click on the settings on the lefthand side of the screen to limit your search to Creative Commons licensed images. You might also try searching among “tags only” or “all text” if your first search doesn’t turn up something useful.

Click on a thumbnail to bring up that image’s Flickr page. You’ll see the license info for the photo on the righthand side of the page. (You may have to scroll down a bit.) Look for the “Actions” button near the top of the page. Click on “View all sizes” to select a larger size for the image. The “large” size usually has sufficient resolution for digital projects. Right click the image to save it to your computer, then insert it into your infographic.

Be sure to attribute the image to its creator! I usually use a line like this:

Image: “Non-Euclidean,” Derek Bruff, Flickr (CC)

R Code for Checking Normality Assumptions

As requested, here’s some R code for checking the normality of a set of data. In the code below, I’ve assigned to the variable x a set of 12 random numbers generated from a normal distribution. For your projects, you’ll already have a set of data to check.

> x <- rnorm(12,0,1)
> x
 [1]  1.45969937  1.06523019 -0.55190387  0.50203983 -0.18073330
 [6]  0.03498171  0.74422040 -0.26451116 -0.99968966 -1.65212671
[11]  1.16201012  0.29497770
> qqnorm(x)
> qqline(x)
> hist(x)
> counts <- vector(mode="numeric",3)
> for (i in 1:3) counts[i] <- length(subset(x,abs(x-mean(x)) < i*sd(x)))/length(x)
> counts
[1] 0.5833333 1.0000000 1.0000000

The above code generated these two plots:

Linear Regression Commands in R

After cleaning up the data you generated in class today a bit more, I was able to run the linear regression commands in R and get sensible results. Here are two CSV files you can use to play around with R:

And here are the R commands I used to generate the plot below:

> math216A <- read.csv("C:/Users/bruffdo/Desktop/math216A.csv")
>   View(math216A)
> height <- math216A$Height
> shoe <- math216A$Shoe
> plot(height,shoe)
> fit <- lm(shoe ~ height)
> abline(fit)
> cor(height,shoe)
[1] 0.4408186
> summary(fit)

lm(formula = shoe ~ height)

    Min      1Q  Median      3Q     Max
-3.7778 -1.1254 -0.2565  0.3380  9.4356 

            Estimate Std. Error t value Pr(>|t|)   
(Intercept) -7.74116    5.49626  -1.408  0.16572   
height       0.26220    0.07872   3.331  0.00171 **
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Residual standard error: 2.351 on 46 degrees of freedom
Multiple R-squared: 0.1943,    Adjusted R-squared: 0.1768
F-statistic: 11.09 on 1 and 46 DF,  p-value: 0.001713

Here’s the R-generated plot of shoe size versus height:

These data have a correlation coefficient of R = 0.44.

Introduction to Pinterest

If you don’t know about Pinterest, you can think of it as an image-based social bookmarking tool. It works a lot like Diigo, except that instead of bookmarking websites, you “pin” images from websites to a virtual pinboard. Since we’ll be dealing with data visualization in this course, a social bookmarking site that emphasizes images is a good match for our needs.

If you do know about Pinterest, you’re probably wondering what the heck I’m doing asking you to use it for your academic work! I know that most people who use Pinterest use it to save and share images they like of craft projects, baking ideas, fashion, and the like. But there’s nothing that says that Pinterest can only be used for such things. It’s a tool for saving and sharing images of all kinds, so why not use it for statistics images?

Either way, to get a sense of how you might use Pinterest in this course, take a look at a couple of my boards on Pinterest, one focusing on visual thinking and one on cryptography.

To get started using Pinterest, head to and request an invitation to join.It can take a couple of days for an invitation to arrive, so go ahead and do this as soon as possible. One you get your invitation via email, you’ll need to create an account on Pinterest using a Facebook or Twitter account.

As I mentioned in my introduction to Diigo, if you use your real, full name on a social bookmarking site, your bookmarks could very well show up when someone Googles your name. That may be great if you have a set of bookmarks that show how smart and interesting you are. But you may want your social bookmarks to be in a more private space. For the purposes of this course, you’re welcome to use a pseudonym for your Pinterest account, as long as you let me know what it is. Since Pinterest accounts are based on Facebook and Twitter accounts, that means you’ll have to create a pseudonymous Twitter account first.

Once you get the invite from Pinterest, just follow the instructions. I won’t go through a bunch of screenshots here. Pinterest is a user-friendly site and its enrollment process is particularly easy to follow.

What’s a little trickier is sharing your course-related “pins” with the rest of the class. Pinterest doesn’t have a group feature like Diigo, so we’ll need to do a little hacking. You’ll need to do two things:

  1. Send me the URL for your Pinterest page.
  2. Include the text “#math216” in the description of all course-related pins.

Then you can look for your course-related pins, along with those from other students in the course, in the right-hand column here on the course blog. If you have any questions about using Pinterest with this course, just let me know.

(If you’re interested in the behind-the-scenes stuff: On my end, I’ll use the very clever web service ifttt (if-this-then-that) to monitor your Pinterest page and copy any pins with “#math216” in them to a dedicated Twitter account (@db_tricorder). The feed for that Twitter account appears in the righthand column here on the course blog, making it easy to see all course-related pins in one place.)


Introduction to Diigo

One of your social bookmarking options is the service Diigo, which has a handy group feature that we’ll use in this course. Here’s what the Math 216 group looks like as I write this:

(Click on the image to see a larger version.)

If you select Diigo as your social bookmarking tool, you’ll share your bookmarks with this group. You’ll also comment on your fellow students’ bookmarks here.

To get started, visit and click on “Join Diigo.”To create an account, you have two options. You can create one from scratch:Or you can use an existing Facebook, Twitter, Google, or Yahoo! account:If you’d rather not use your real, full name, you’re welcome to choose a pseudonym. In that case you’ll probably want to create an account from scratch so you can avoid using your real name. Please note that your bookmarks will be on the open Web, so there’s a chance a Google search on your full name will lead to your Diigo bookmarks. That might be a good thing as you establish your professional presence online, but you’re welcome to avoid that by choosing a pseudonym.

Once you’ve created your account and verified it via email, you’ll see a welcome message with options for adding Diigo tools to your Web browser:Diigo requires you to install one of these two browser tools to get started. I suggest you go with Option 2 (the “feature-rich Diigo toolbar”) since it makes it easy to save a bookmark to a Diigo group, which you’ll need to do in this course. You’re welcome, however, to use either option.

Once you’ve installed a browser tool, navigate your browser to some Web page and use your browser tool to bookmark it. You’ll get a pop-up window that looks something like this:Diigo loads the page title for you, and suggests some tags you might use. Tags are optional, but the more tags you use for a bookmark, the easier it will be to find later. Go ahead and save your bookmark.

Head back to and click on “Get Started Now!”, as seen here:That will take you to your Diigo library:This is your homebase within Diigo. From here you can view and edit your bookmarks. The navigation at the left is very useful for finding old bookmarks.

Next, you’ll need to join the Math 216 Diigo group. Visit the group page to see this:Click on the button that says “Apply to join this group.” I have this group set up so that I (the group owner) must approve any new members. This way I can keep out people who aren’t in our course. Go ahead and request to join the group.  Be sure to include a message to me so I know you’re a student in this course and not some passerby. I’ll approve your request as soon as I get the chance.

One last thing to know: When you bookmark something for this course, you need to add it to the Math 216 group so the rest of us can find it. To do so, click on “More Options” in the pop-up window you use to bookmark something:You’ll see a checkbox that reads “Share to a Group.” Click on this and select the Math 216 group before hitting save.

That’s it for now. If you have any questions about getting started with Diigo, please ask me or the TAs.