# First steps

`# Marco Plebani 18 May 2018`

```########################################## ##### OUR FIRST R SCRIPT ################# ##########################################```

```# you run code by selecting lines and pressing control+R (windows) or cmd+enter (mac) # lines starting with an ash (like this one) don't "run". # Useful for writing comments or for deactivating bits of code without deleting them.```

```# R is first of all a powerful calculator! # try:```

```3*2 10/15 sqrt(2) # square root of two # sqrt() is the first R function you see! Functions apply to what's between the brackets sqrt() # no argument between the brackets? R gets angry. Don't anger R. pi # useful 2^3 # two to the third power exp(1) # this equals to e^1 log(1) # natural log log(exp(1)) log10(10) # decimal log```
``` # you can save results. Just give it a name as follows: myfirstRobject <- 10/15 myfirstRobject mysecondone <- 11*11 myfirstRobject + mysecondone```

```# want to apply a calculation to more than one number at a time? # save some numbers in an R object called "vector": somenumbers <- c(1,2,3,5,7,11) somenumbers*2```

```# a bunch of vectors together is called a matrix. # unless you give each vector a name. In that case they form an object called a "data frame" (namely a dataset). Hese's how you create one:```

```myfirstdf <- data.frame(mynumbers = somenumbers) # now create a new column for the data.frame: myfirstdf\$timestwo <- myfirstdf\$mynumbers * 2 # Do you want to export a data.frame? Easy peasy! write.csv(myfirstdf, "~/Desktop/output.csv") # I am working on a Mac. You may have to type directories in a slightly different way in Windows.```