```{r setup, include=FALSE}
knitr::opts_chunk$set(echo=TRUE, fig.align="center")
```

#### Statistics for Laboratory Scientists ( 140.615 )

## R as a calculator

The below is based in part on a script from John Fox.

#### Basic arithmetic 

```{r}
2+3
2-3
2*3
2/3
2^3
```

#### Precedence of operators

```{r}
4^2-3*2
(4^2)-(3*2) # better: use parentheses to group and clarify
4^(2-3)*2
1-6+4
2^-3
2^(-3)
-2--3
(-2)-(-3)
```

#### Functions, obtaining help

```{r}
log(100)
?log
help(log)
log(100,base=10)
log(100,b=10)
log(100,10)
log10(100)
help.search("log")
??log
```

#### Vectorized arithmetic

```{r}
c(1,2,3,4) 
1:4   
4:1
-1:2 # note the precedence
(-1):2
seq(1,4)
seq(2,8,by=2)
seq(0,1,by=0.1)
seq(0,1,length=11)
c(1,2,3,4)/2    
c(1,2,3,4)/c(4,3,2,1)
log10(c(0.1,1,10,100))
log2(c(1,2,4,8,16,32))
```

#### Basic summaries.

```{r}
x <- c(1,3.5,-28.4,10)
x
sum(x)
prod(x)
mean(x)
```

#### Missing data points.

```{r}
x <- c(1,5,10,NA,15)
x
sum(x)
sum(x,na.rm=TRUE)
prod(x,na.rm=TRUE)
mean(x,na.rm=TRUE)
```

#### More on creating simple vectors

```{r}
rep(2,10)
rep(1:3,4)
rep(1:3,c(4,4,4))
rep(1:3,rep(4,3))
rep(1:3,each=4)
rep(c(1,2,3),c(2,4,5))
```

#### Numeric, character, logic.

```{r}
c(1,3.5,-28.4,10)
c("cat","dog","mouse","monkey")
c(TRUE,TRUE,TRUE,FALSE,FALSE)
```