# Basic Logical Expressions and Curly Brackets in R – Baiting

In the past two weeks, I went through more tutorials and learned how to select, sort, and rank columns in a matrix or a data frame. However, I am more thrilled to talk about the “if-else” logic expression as I noticed something strange while trying out myself. If you are interested in studying this topic yourself, you may find this edx video tutorial and this website to be helpful. They are both free.

The first thing I entered was:

This is the simplest “if-else” expression. The first line means set “a” as a variable and a = 2. The third to the fifth line is the logic expression. If “a” doesn’t equal to 0 (in R, “!=” means “≠”）, the output would be 1/a. Otherwise (if a = 0), the output should be “FALSE”. This is what happens when we run these lines.

Obviously, the logic works. We have a = 2, so a ≠ 0. This matches with the condition that the result = 1/a = 1/2 = 0.5. However, if we start “else” in a new line, then something strange will happen.

When we start “else” in a new line, the R Studio says there is an error. If we run the codes, R Console would show the following:

This triggers my curiosity, since this is the only time that starting a new line would lead to different results. Let me explain it quickly using another example.

In R, the two sections in Code 3 mean exactly the same thing. The only difference is the first section occupies 1 line while the second section occupies 4. They both mean read the document “oasis_cross-sectional.csv” as a data frame and name the data frame as “A”. This example is not an exception. In fact, starting codes from a new line work in most expressions I learned. However, it doesn’t work in the “if-else” expression. To figure out the answer, I did some research on the curly bracket “{” and “}” in R.

According to “R in a Nutshell, 2nd Edition” by Joseph Adler, curly brackets (braces) are “used to evaluate a series of expression” or “used to group a set of operations in the body of a function” (Adler). This hints that the curly brackets only work when there is another corresponding expression, like “if-else. ” If there is no such expressions, curly brackets would have no effects.

Why this matters? Obviously, curly brackets only work when you have pairs of heads and tails. The computer only reads the statement in between. Here is an example:

If you compare Code 4 and Code 5, you would notice Code 4 is missing the tail curly bracket ( } ). So, your computer would read Code 4 as a bunch of characters and Code 5 as a statement.

Again, curly brackets need to work with another expression. My hypothesis is the head bracket would find the first expression in front of itself and match with it. Then, the corresponding tail bracket will close the statement. This explains why Code 1 works when we have started the head bracket in a new line. The bracket would automatically find the “if” expression and match with it.

However, the “else” expression doesn’t do the same work. When you start “else” in a new line, it wouldn’t find the corresponding “if.” I believe this is not a flaw, but an intentional design. A head bracket always needs another expression, but “else” doesn’t always need “if”, it may match with other expressions, like “else if”. So letting “else” find its own expression would lead to many logic errors.

To test my conclusion, I used the following codes:

In Code 6, the highlighted lines are the ones I inserted intentionally for testing. According to our hypothesis, the first head curly bracket in line 9 would find the statement in front of it. This means line 7 would match with line 9. At the same time, the “if” expression in line 3 would match with line 5, as after we give the condition (a > 6), it automatically considers line 5 as the “so what.” This is what happens when we run the codes:

Only the first line works! The logic function “if-else” fails as the brackets can no longer find the correct expression. In comparison to Code 2 and Output 2, even though R identify both errors as “unexpected ‘else’,” it is obvious that the problem with Code 2 is the tail bracket while the problem with Code 6 is the head bracket. In addition, line 7 fails to work as line 5. Line 5, the line that is supposed to match with line 7, is now matched with line 3 (as shown by the “+” sign in the output). This means we no longer have a definition for A, so we can’t find it.

This is the end of my main topic. In this blog, we successfully found a problem and established some reasonable conclusions. Of course, these conclusions may be wrong, but the process of identifying and solving a problem was fun for me! When codes fail to run, I believe it is always important to read the error notice to identify the issue. Furthermore, it is also helpful to reflect on and identify the deeper reason that leads to the error.

Works Cited

Adler, Joseph. R in a Nutshell. 2nd ed., Sebastopol, O’Reilly Media, 2012. O’REILLY, http://www.oreilly.com/library/view/r-in-a/9781449358204. Accessed 29 Apr. 2019.

“ifelse.” RDocumentation, www.rdocumentation.org/packages/base/versions/3.5.3/topics/ifelse. Accessed 29 Apr. 2019.

Irizarry, Rafael. “Basic Conditionals.” Edx.org. Lecture.

I have just received word back from ATCC regarding my cell lines and the contamination issue I faced. They said they are unwilling to give a refund on my cells because the tests they had previously run showed no signs of contamination. However, they did offer me a 10% discount from the original \$492.00 it costs to purchase the cell line. I am going to discuss with Teacher Margaret regarding the state of my project since this will be the third time to purchase cells and roughly a 5 weeks is in not enough time to get cells confluent and run all of the tests I had initially planned. Additionally, it is very frustrating to have ATCC not refund or send me a new cell line since the tests we ran showed no signs of contamination on our part. This was not how I expected my project to be carried out and has been a very difficult and stressful time for me to figure out logistics regarding this project.

After discussing with T. Margaret we have decided that it may be best for me to write out the cell culturing procedures necessary for the NBT-ii cell line should a student wish to continue this project in coming years.

# RSA Algorithm – Baiting

In this blog, I would like to provide updates on the M3 Challenge and my research project in Abstract Algebra for Chester County Science Fair. Then, I will introduce the RSA Algorithm, the most used information encryption algorithm in the world and how it relates to my project.

# Fake It Till You Make It

Inova Consultancy

I’ve been struggling to breathe recently: masks can be suffocating. I’ve just been putting on the face of the perfect CEO who has the best website, the best social media page, and the best articles. But the reality is that I have been exhausted recently. Additionally, I have been talking to other non-profits who are huge So what do I do? So It seems as if I have been fakin’ it till’ I’m makin’ it in two ways: pretending I am not tired and pretending we are a bigger organization. Continue reading

# Medicine in 19th Century Europe– Yuchen

~ 19th Century Europe ~

In the 19th century, western medicine experienced major changes and advancements because of the industrialization and urbanization that created both ideal condition for various diseases to break out as well as the opportunity for the discovery of new medical knowledge and development of new treatment methods. Continue reading

# An introduction to human vision: How do we see? – Andy

Vision is a prominent part of our sensations. A world that nobody can see will no doubt be chaotic. In fact, visions have been one of the most direct emotional drives in daily life. So how does Nature put everything together so that human beings can see? Continue reading

# How I Redefine Addition – Baiting

In my last blog, I talked about my plan for the semester, why I want to study abstract algebra, and some basic concepts involving mapping. In this blog, I will first provide some update on Modeling the Future, a team math competition we have been working on, and how I redefine addition in group theory. I will also talk about my plan for the science fair. Continue reading

# Cognitive Science: An Introduction – Andy

Hello there! My name is Andy Chen, a current Senior at Westtown school. This semester, I plan to take an independent science course to furthers my interests in Cognitive Science. Let’s get started!

## So first, what is Cognitive Science?

When Cognitive Science first emerged in the late 1900s, scientists were unsure about its domain: was it “Cognitive Psychology under a new name,” or “an offshoot of artificial intelligence?” (Estes, 1991, p. 282). Continue reading

# Abstract Algebra: A NEW Start – Baiting

In this blog, I would like to briefly review my Fall semester and share my plan for the Spring.

In the past four months, I worked on Differential Equations and its related topics. Through following the MIT Open Course Ware, I learned different methods to solve DEs and their implications in real life.