Measure of spread around the circle. It should be noted that: If R=0, then the data is completely spread around the circle. If R=1, the data is completely concentrated on one point.

## References

Mardia, K.V. (1972). Statistics of Directional Data: Probability and Mathematical Statistics. London: Academic Press.

## Examples

```
# Example data from Davis (1986), pp. 316
finland_stria <- c(
23, 27, 53, 58, 64, 83, 85, 88, 93, 99, 100, 105, 113,
113, 114, 117, 121, 123, 125, 126, 126, 126, 127, 127, 128, 128, 129, 132,
132, 132, 134, 135, 137, 144, 145, 145, 146, 153, 155, 155, 155, 157, 163,
165, 171, 172, 179, 181, 186, 190, 212
)
mean_resultant_length(finland_stria, w = NULL, na.rm = FALSE) # 0.800
#> [1] 0.8003694
```