First steps

# Marco Plebani 18 May 2018

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##### OUR FIRST R SCRIPT #################
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# 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.

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