---
author: "Write your name here"
number: STUDENT_NUMBER
title: "Homework 2"
subtitle: "Computing in Molecular Biology 1 – Molecular Biology and Genetics Department"
description: "First rehearsal for Midterm Exam"
date: "November 9, 2020"
output: 
  html_document: 
    number_sections: yes
    self_contained: no
---

# Creating vectors

## Write the R command to produce this vector
```{r q1}
# write your answer here
```

## Write the R command to produce a vector with numbers 0, 0.1, 0.2, …, 0.9, 1.0
```{r q2}
# write your answer here
```

## Create a named vector, with the values 1, 2, 3, and 4, and with names "one", "two", "three", and "four".
Assign this vector to the variable `x`. Then show the content of `x`
```{r q3}
# write your answer here
```

## Using the name as index, show the value of `two` in the vector `x`
```{r q4}
# write your answer here
```


# Using indices
Your R system has already some vectors to be used for exercises. One of them is `letters`, containing the English alphabet

## Write the command to show the content of `letters`
```{r q5}
# write your answer here
```

## Find the second element
```{r q6}
# write your answer here
```

## Find the 10th element
```{r q7}
# write your answer here
```

## Make a logic vector that is `TRUE` for the vowels in `letters`. In English the vowels are `c("a", "e", "i", "o", "u")`
```{r q8}
# write your answer here
```

## Find the last element
```{r q9}
# write your answer here
```

## Find the first 6 elements
```{r q10}
# write your answer here
```

## Find the last 6 elements
```{r q11}
# write your answer here
```

## Find all except the first 3 elements
```{r q12}
# write your answer here
```

## Find the elements in positions 5, 7, 9, …, 15
```{r q13}
# write your answer here
```


# USA states
Other vectors already included in R are used to describe USA states. They include `state.area` and `state.name`, which we will use in this exercise.

In the future we will work with other countries' data, but these are easier to use for this homework.

## Write the R command to create a logic vector, which is `TRUE` for the elements of `state.area` that are greater than 5E4
```{r q14}
# write your answer here
```

## Show the first 4 elements of the vector `state.name`
```{r q15}
# write your answer here
```

## Show all the elements of the vector `state.name`, except the first 40
```{r q16}
# write your answer here
```

## Show the elements of the vector `state.name` corresponding to states whose area is greater than 2E5
```{r q17}
# write your answer here
```


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