# Use and Modify (Functions)

The length of an organism is typically strongly correlated with its body mass. This is useful because it allows us to estimate the mass of an organism even if we only know its length. This relationship generally takes the form:

mass = a * length^b

Where the parameters `a`

and `b`

vary among groups. This allometric approach is
regularly used to estimate the mass of dinosaurs since we cannot weigh something
that is only preserved as bones.

The following function estimates the mass of an organism in kg based on its
length in meters for a particular set of parameter values, those for *Theropoda*
(where `a`

has been estimated as `0.73`

and `b`

has been estimated as `3.63`

;
Seebacher 2001).

```
get_mass_from_length_theropoda <- function(length){
mass <- 0.73 * length ^ 3.63
return(mass)
}
```

- Use this function to print out the mass of a Theropoda that is 16 m long based on its reassembled skeleton.
- Create a new version of this function called
`get_mass_from_length()`

that takes`length`

,`a`

and`b`

as arguments and uses the following code to estimate the mass`mass <- a * length ^ b`

. Use this function to estimate the mass of a Sauropoda (`a = 214.44`

,`b = 1.46`

) that is 26 m long.

*Expected outputs for Use and Modify:*

*1*