ShadCR {FSAdata} | R Documentation |

## Ages of American Shad assigned from scales by three readers at two times.

### Description

Ages of American Shad (*Alosa sapidissima*) assigned from scales by three readers at two times.

### Format

A data frame with 53 observations on the following 8 variables.

- fishID
A unique fish identification number

- trueAge
The true age of the fish

- agerA1
Ages assigned by reader A at time 1

- agerA2
Ages assigned by reader A at time 2

- agerB1
Ages assigned by reader B at time 1

- agerB2
Ages assigned by reader B at time 2

- agerC1
Ages assigned by reader C at time 1

- agerC2
Ages assigned by reader C at time 2

### Details

The true ages for fish in their sample were known because the Shad had been marked prior to being stocked. Additionally, 13 biologists twice (independently) estimated the age from scales for each fish. The known age of the fish (`trueAge`

) and the age estimates from three of the 13 biologists are available in this data.frame. The estimated age variables are labeled with `ager`

, a letter for the three biologists (`A`

, `B`

, or `C`

) and a number for which time the scale was interpreted (`1`

or `2`

). Some biologists chose not to assign an age to some scales and, thus, those data are missing (shown as `NA`

values).

### Topic(s)

Age Comparison

Age Precision

Age Bias

Ageing Error

### Note

Used in the Introductory Fisheries Analyses with R book.

### Source

From McBride, R.S., Hendricks, M.L., and Olney, J.E. 2005. Testing the validity of Cating's (1953) method for age determination of American Shad using scales. Fisheries, 30:10-18. Obtained directly from Rich McBride.

### Examples

data(ShadCR)
str(ShadCR)
head(ShadCR)
op <- par(mfrow=c(2,2),pch=19)
plot(agerA1~agerA2,data=ShadCR)
plot(agerB1~agerB2,data=ShadCR)
plot(agerC1~agerC2,data=ShadCR)
plot(agerA1~agerB1,data=ShadCR)
par(op)

[Package

*FSAdata* version 0.3.7

Index]