---
title: "R Notebook"
output: html_notebook
---

This is an [R Markdown](http://rmarkdown.rstudio.com) Notebook. When you execute code within the notebook, the results appear beneath the code. 

Try executing this chunk by clicking the *Run* button within the chunk or by placing your cursor inside it and pressing *Cmd+Shift+Enter*. 

```{r}
plot(cars)
```

Add a new chunk by clicking the *Insert Chunk* button on the toolbar or by pressing *Cmd+Option+I*.

When you save the notebook, an HTML file containing the code and output will be saved alongside it (click the *Preview* button or press *Cmd+Shift+K* to preview the HTML file).

```{r}
2+3
2*3*4
sqrt(10)
pi * pi
```

plot() is equivalent to a graphical plot
c() creates a list by concatenating the numbers into a single vector object
```{r}
plot(c(1,3,5,6))
```

plot() with 2 lists is equivalent to a "scatter plot""
```{r}
plot(c(1,3,5,6),c(2,4,6,3))
```

Commands: help(), apropos(), help.search()
```{r}
help(plot)
apropos("sort")
help.search("sort")
```

for each amount that an elastic band is stretched, we measure the distance traveled by the band when released. 
```{r}
elasticBand <- data.frame(stretch = c(46, 54, 48, 50, 44, 42, 52),
                          distance = c(148, 182, 173, 166, 109, 141, 166))
# print(elasticBand)
summary(elasticBand)
```

how to quit
```{r}
rm(elasticBand)
rm(C)
rm(F)
# quit()
```

converting C to F
```{r}
Ce <- 25:30
Fa <- 9/5*Ce+32
C2F <- data.frame(Celsius=Ce, Fahrenheit=Fa)
print(C2F)
```

VECTORS
```{r}
c(2,6,5)
```
```{r}
3:10
```
```{r}
X <- c(T,F,T,T)
X
```
```{r}
Y <- c("Alice", "Bob", "Cathy")
Y
```
```{r}
Z <- c(X,Y)
Z
```

missing data
```{r}
X <- c(1, NA, 3, 0, NA)
X
```

transforming missing data
```{r}
X[is.na(X)] <- 0
X
```

First install DAAG - a collection of data for our experiments
```{r}
library(DAAG)         # load DAAG package
data(Cars93.summary)  # copy Cars93.summary into workspace
Cars93.summary
```

```{r}
data(airquality)
# names(airquality) # variables in this data frame
summary(airquality)
# airquality
sapply(airquality, mean) # apply to each column of data frame
```

```{r}
# plotting a scatter plot
attach(airquality) # applies the next plot command to this data frame
plot(Ozone, Wind)
detach(airquality)
```

```{r}
# plotting a scatter plot
attach(airquality) # applies the next plot command to this data frame
plot(Ozone, Wind)
detach(airquality)
```

```{r}
data(possum) # copy possum into workspace
fossum <- possum[possum$sex == "f", ] # pick the females
par(mfrow = c(1,2))
attach(fossum)
hist(totlngth, breaks = 72.5 + (0:5) * 5, ylim = c(0, 22),
     xlab = "Total length", main = "A: Breaks at 72.5, 77.5, ...")
hist(totlngth, breaks = 75 + (0:5) * 5, ylim = c(0, 22),
     xlab = "Total length", main = "B: Breaks at 75, 80, ...")
```

```{r}
dens <-density(totlngth)
xlim <-range(dens$x); ylim <- range(dens$y)
par(mfrow = c(1,2))
hist(totlngth, breaks = 72.5 + (0:5) * 5, probability = T,
     xlim = xlim, ylim = ylim,
     xlab = "Total length", main = "C: Breaks at 72.5, 77.5, ...")
lines(dens)
hist(totlngth, breaks = 75 + (0:5) * 5, probability = T,
     xlim = xlim, ylim = ylim,
     xlab = "Total length", main = "D: Breaks at 75, 80, ...")
lines(dens)
# detach(fossum)
```

