```{r}
# one possibility: type the data in
d <- data.frame(
  location= c("Quito", "Capehope", "Rome",  "Paris", "Lapland"),
  x=        c(0.0000,   0.2987,    0.4648,  0.5762,   0.8386),
  y=        c(51,       337,       279,     374,      722)
  )
print(d)
rm(list=ls())
```

```{r}
# some data comes with R, you don't want to think too much about this
summary(cars)
ls()
# data()
# help(data)
cars <- cars
ls()
rm(list=ls())
```

```{r}
# data in a package, a more orderly built-in
# Data Boscovich used to estimate the ellipticity of the earth.
# 1755
library('quantreg')
search()
# data(package='quantreg')
# help(Bosco)
data(Bosco)
ls()
print(Bosco)
rm(list=ls())
```

```{r}
# Reading from a TSV file
d <- read.table('Boscovich.tsv',header=TRUE,sep='\t',stringsAsFactors=FALSE)
print(d)
rm(list=ls())
```

```{r}
# save in a few forms for later use
# to clear: rm -rf Boscovich.Rds Boscovich.SQLite Boscovich.h2db*
d <- read.table('Boscovich.tsv',header=TRUE,sep='\t',stringsAsFactors=FALSE)
saveRDS(d,'Boscovich.Rds')
library('RSQLite')
con <- dbConnect(SQLite(),'Boscovich.SQLite')
rs <- dbSendQuery(con,'CREATE TABLE Boscovich (location TEXT, x REAL, y REAL)')
dbClearResult(rs)
rs <- dbSendPreparedQuery(con,'INSERT INTO Boscovich VALUES (?,?,?)',d)
dbClearResult(rs)
dbDisconnect(con)
options( java.parameters = "-Xmx2g" )
library('RJDBC')
drv <- JDBC('org.h2.Driver','h2-1.3.176.jar',identifier.quote='"')
con <- dbConnect(drv,'jdbc:h2:Boscovich.h2db')
dbWriteTable(con,'Boscovich',d)
dbDisconnect(con)
rm(list=ls())
```


```{r}
# Reading a native R save
d <- readRDS('Boscovich.Rds')
print(d)
rm(list=ls())
```

```{r}
# read directly from Microsoft Excel
library('gdata')
dA <- read.xls('Boscovich.xlsx',sheet=1,
               header=FALSE,stringsAsFactors=FALSE,
               as.is=TRUE,colClasses='character')
print(dA)
d <- dA[c(-1,-2),-1]
colnames(d) <- dA[2,-1]
for(cn in colnames(d)) {
  d[[cn]] <- type.convert(d[[cn]],as.is=TRUE)
}
print(d)
rm(list=ls())
```

```{r}
# read from SQLite
library('RSQLite')
con <- dbConnect(SQLite(),'Boscovich.SQLite')
rs <- dbSendQuery(con,'SELECT * FROM Boscovich')
d <- fetch(rs,-1)
dbClearResult(rs)
dbDisconnect(con)
print(d)
rm(list=ls())
```

```{r}
# read from a JDBC connection to an arbitrary database
options( java.parameters = "-Xmx2g" )
library('RJDBC')
drv <- JDBC('org.h2.Driver','h2-1.3.176.jar',identifier.quote='"')
con <- dbConnect(drv,'jdbc:h2:Boscovich.h2db')
d <- dbGetQuery(con,'SELECT * FROM Boscovich')
dbDisconnect(con)
print(d)
rm(list=ls())
```

```{r}
# treat a data frame as a SQL database table
options(gsubfn.engine = "R") # prevent a crashing attempt to start X11 on OSX
library('sqldf')
d <- read.table('Boscovich.tsv',header=TRUE,sep='\t',stringsAsFactors=FALSE)
dj <- sqldf('
   SELECT
      d1.location location1,
      d2.location location2,
      d2.x-d1.x deltax,
      d2.y-d1.y deltay
   FROM
      d d1
   JOIN
      d d2
')
class(dj)
print(dj)
rm(list=ls())
```