mamquam | R Documentation |

Size of gravels collected from a sandbar in the Mamquam River, British Columbia, Canada. Summary data, giving the frequency of observations in 16 different size classes.

`data(mamquam)`

The `mamquam`

data frame has 16 rows and 2 columns.

[, 1] | midpoints | midpoints of intervals (psi units) |

[, 2] | counts | number of observations in interval |

Gravel sizes are determined by passing clasts through templates of particular sizes. This gives a range in which the size of each clast lies. Sizes (in mm) are then converted into psi units by taking the base 2 logarithm of the size. The midpoints specified are the midpoints of the psi unit ranges, and counts gives the number of observations in each size range. The classes are of length 0.5 psi units. There are 3574 observations.

Rice, Stephen and Church, Michael (1996)
Sampling surficial gravels: the precision of size distribution
percentile estimates.
*J. of Sedimentary Research*,
**66**, 654–665.

```
data(mamquam)
str(mamquam)
attach(mamquam)
### Construct data from frequency summary, taking all observations
### at midpoints of intervals
psi <- rep(midpoints, counts)
barplot(table(psi))
### Fit the hyperbolic distribution
hyperbFit(psi)
### Actually hyperbFit can deal with frequency data
hyperbFit(midpoints, freq=counts)
```

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