Some diet studies record small amounts of a prey item as "trace". These are encoded in the diet database using the value -999. This function replaces those entries with the nominated numeric value.
replace_trace_values(x, replace_with = 0)
| x | data.frame: diet data, as returned by  | 
|---|---|
| replace_with | numeric: value to use as a replacement for "trace" values | 
data.frame