## Graphing

# Adult vs Newborn Size

It makes sense that larger organisms have larger offspring, but what the
mathematical form of this relationship should be is unclear. Let’s look at the
problem empirically for mammals.

Download some
mammal life history data
from the web. You can do this either directly in the program using `read.csv()`

or download the file to your computer using your browser, save it in the `data`

subdirectory, and import it from there. It is tab delimited so you’ll want to
use `sep = "\t"`

as an optional argument when calling `read.csv()`

. The `\t`

is
how we indicate a tab character to R (and most other programming languages).

When you import the data there are some extra blank lines at
the end of this file. Get rid of them by using the optional `read.csv()`

argument `nrows = 1440`

to select the valid 1440 rows.

Missing data in this file is specified by `-999`

and `-999.00`

. Tell R that
these are null values using the optional `read.csv()`

argument,
`na.strings = c("-999", "-999.00")`

. This will stop them from being plotted.

- Graph adult mass vs. newborn mass. Label the axes with clearer labels than
the column names.
- It looks like there’s a regular pattern here, but it’s definitely not
linear. Let’s see if log-transformation straightens it out. Graph adult mass
vs. newborn mass, with both axes scaled logarithmically. Label the axes.
- This looks like a pretty regular pattern, so you wonder if it varies among
different groups. Graph adult mass vs. newborn mass, with both axes scaled
logarithmically, and the data points colored by order. Label the axes.
- Coloring the points was useful, but there are a lot of points and it’s kind
of hard to see what’s going on with all of the orders. Use
`facet_wrap`

to
create subplot for each order.
- Now let’s visualize the relationships between the variables using a simple
linear model. Create a new graph like your faceted plot, but using
`geom_smooth`

to fit a linear model to each order. You can do this using the
optional argument `method = "lm"`

in `geom_smooth`

.

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