magrittr.Rmd

---
title: "Magrittr"
output: pdf_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)

library(magrittr) # %>%

```

# The Pipe %>%

```{r normalPipe}

# General operation moving forward
# CTRL-SHIFT-M

c(5,4,2,6,3,4,3,4,6) %>%
    mean()

mean(c(5,4,2,6,3,4,3,4,6))

# The pipe is like the unix command line pipe, 
#   take output of left and pipe into the right
# The pipe in R differs in that you can break lines 
#   and it doesnt need to be STDIN or STDOUT

#------------------------------------------------#

# Taking a forward moving operation and assigning it to a variable 

# read this as:
#   "X receives the value of the vector going through the mean function"

x <- c(5,4,2,6,3,4,3,4,6) %>% 
    mean()

cat("the value of x is: ", x)
```

# The Compound Pipe %<>%

```{r compoundPipe}

# Normal pipe pushes results forward through processes 
#   the compound pipe pushes the operation forward but also assigns the result 
#       back to the initial object, basically it becomes '<-' 

# first y contains this vector of numbers
y <- c(5,4,2,6,3,4,3,4,6)

# Then we compound pipe that vector into the mean function and the result of 
#   the mean function is then re-assigned to y, akin to:
#       y = mean(y)
y %<>% mean()

cat("the value of y is: ", y)
```

# The Exposition Pipe %$%

```{r espositionPipe}

# When piping this tribble forward it assumes i want to 
#   calculate the mean of both vectors

tibble::tribble(
    ~name, ~age,
    "john", 26,
    "karen", 54,
    "susan", 45,
    "joe", 16
) %>%
    mean(age) # this does not work

#------------------------------------------------#

# when using the exposition pipe %$% it allows you to use the names of the 
#   content on the 'left hand side' of the piping operation and therefore 
#       reference only the numeric vector in the mean function.

# so what appears in the mean function is equivalently exampleTribble$age

tibble::tribble(
    ~name, ~age,
    "john", 26,
    "karen", 54,
    "susan", 45,
    "joe", 16
) %$%
    mean(age) # and so this works

```

# the Tee pipe

```{r teePipe}

# pipe a a value forward but return the original value

#        value -------------> into a function (This is not returned)
#                    |
#                    |
#                    |
#                    |
#                    |
#                    V
#                    Returned Result


# value is piped into the mean function but only vector is returned
c(5,4,2,6,3,4,3,4,6) %T>% mean() # Shows only the vector

# This is useful when an expression is used for its side-effect, say plotting or printing.
c(5,4,2,6,3,4,3,4,6) %T>% plot() # shows the vector and the plot

```