# intervalGRdiff

##### Calculates the growth rates for a specified time interval

Using the values of the responses, calculates the specified combination of the Absolute Growth Rates using differences (AGR), the Proportionate Growth Rates (PGR) and Relative Growth Rates using log differences (RGR) between two nominated time points.

##### Usage

```
intervalGRdiff(responses, individuals = "Snapshot.ID.Tag",
which.rates = c("AGR","PGR","RGR"), suffices.rates=NULL,
times.factor = "Days", start.times, end.times, suffix.interval,
data)
```

##### Arguments

- responses
A

`character`

giving the names of the columns in`data`

from which the growth rates are to be calculated.- individuals
A

`character`

giving the name(s) of the`factor`

(s) that define the subsets of the`data`

for which each subset corresponds to the`responses`

for an individual.- which.rates
A

`character`

giving the growth rates that are to be calculated. It should be a combination`"AGR"`

,`"PGR"`

and`"RGR"`

.- suffices.rates
A

`character`

giving the characters to be appended to the names of the responses in constructing the names of the columns containing the calculated growth rates. The order of the suffices in`suffices.rates`

should correspond to the order of the elements of`which.rates`

.- times.factor
A

`character`

giving the name of the column in`data`

containing the factor for times at which the data was collected. Its levels will be used in calculating growth rates and should be numeric values stored as characters.- start.times
A

`numeric`

giving the times, in terms of levels of`times.factor`

, that will give a single value for each`Snapshot.ID.Tag`

and that will be taken as the observation at the start of the interval for which the growth rate is to be calculated.- end.times
A

`numeric`

giving the times, in terms of levels of`times.factor`

, that will give a single value for each`Snapshot.ID.Tag`

and that will be taken as the observation at the end of the interval for which the growth rate is to be calculated.- suffix.interval
A

`character`

giving the suffix to be appended to`response`

to form the names of the columns containing the calculated the growth rates.- data
A

`data.frame`

containing the column from which the growth rates are to be calculated.

##### Details

The `AGR`

is calculated as the difference between the values of
`response`

at the `end.times`

and `start.times`

divided by the
difference between `end.times`

and `start.times`

.
The PGR is calculated as the ratio of `response`

at the `end.times`

to that at `start.times`

and the ratio raised to the power of the
reciprocal of the difference between `end.times`

and `start.times`

.
The `RGR`

is calculated as the `log`

of the PGR and so is equal to
the difference between the logarithms of `response`

at the `end.times`

and `start.times`

divided by the difference
between `end.times`

and `start.times`

.

##### Value

A `data.frame`

with the growth rates.
The name of each column is the concatenation of (i) one of
`responses`

, (ii) one of `AGR`

, `PGR`

or `RGR`

,
or the appropriate element of `suffices.rates`

, and (iii)
`suffix.interval`

, the three components being separated by
full stops.

##### See Also

`intervalGRaverage`

, `intervalWUI`

, `getTimesSubset`

, `GrowthRates`

, `splitSplines`

, `splitContGRdiff`

##### Examples

```
# NOT RUN {
data(exampleData)
Area.smooth.GR <- intervalGRdiff("Area.smooth", which.rates = c("AGR","RGR"),
start.times = 31, end.times = 35,
suffix.interval = "31to35",
data = longi.dat)
# }
```

*Documentation reproduced from package growthPheno, version 1.0-13, License: GPL (>= 2)*